Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Point out that behavior might be switched on 2015 and 2018 too one day

Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.

cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Pkgsrc changes:
 * Bump bootstrap requirements to 1.52.1
 * Adjust patches, adapt to upstream changes, adjust cargo checksums
 * If using an external llvm, require >= 10.0

Upsteream changes:

Version 1.53.0 (2021-06-17)
============================

Language
-----------------------
- [You can now use unicode for identifiers.][83799] This allows
  multilingual identifiers but still doesn't allow glyphs that are
  not considered characters such as `#` (diamond) or `<U 1F980>`
  (crab). More specifically you can now use any identifier that
  matches the UAX #31 "Unicode Identifier and Pattern Syntax" standard. This
  is the same standard as languages like Python, however Rust uses NFC
  normalization which may be different from other languages.
- [You can now specify "or patterns" inside pattern matches.][79278]
  Previously you could only use `|` (OR) on complete patterns. E.g.
  ```rust
  let x = Some(2u8);
  // Before
  matches!(x, Some(1) | Some(2));
  // Now
  matches!(x, Some(1 | 2));
  ```
- [Added the `:pat_param` `macro_rules!` matcher.][83386] This matcher
  has the same semantics as the `:pat` matcher. This is to allow `:pat`
  to change semantics to being a pattern fragment in a future edition.

Compiler
-----------------------
- [Updated the minimum external LLVM version to LLVM 10.][83387]
- [Added Tier 3\* support for the `wasm64-unknown-unknown` target.][80525]
- [Improved debuginfo for closures and async functions on Windows MSVC.][83941]

\* Refer to Rust's [platform support page][platform-support-doc] for more
information on Rust's tiered platform support.

Libraries
-----------------------
- [Abort messages will now forward to `android_set_abort_message` on
  Android platforms when available.][81469]
- [`slice::IterMut<'_, T>` now implements `AsRef<[T]>`][82771]
- [Arrays of any length now implement `IntoIterator`.][84147]
  Currently calling `.into_iter()` as a method on an array will
  return `impl Iterator<Item=&T>`, but this may change in a
  future edition to change `Item` to `T`. Calling `IntoIterator::into_iter`
  directly on arrays will provide `impl Iterator<Item=T>` as expected.
- [`leading_zeros`, and `trailing_zeros` are now available on all
  `NonZero` integer types.][84082]
- [`{f32, f64}::from_str` now parse and print special values
  (`NaN`, `-0`) according to IEEE RFC 754.][78618]
- [You can now index into slices using `(Bound<usize>, Bound<usize>)`.][77704]
- [Add the `BITS` associated constant to all numeric types.][82565]

Stabilised APIs
---------------
- [`AtomicBool::fetch_update`]
- [`AtomicPtr::fetch_update`]
- [`BTreeMap::retain`]
- [`BTreeSet::retain`]
- [`BufReader::seek_relative`]
- [`DebugStruct::non_exhaustive`]
- [`Duration::MAX`]
- [`Duration::ZERO`]
- [`Duration::is_zero`]
- [`Duration::saturating_add`]
- [`Duration::saturating_mul`]
- [`Duration::saturating_sub`]
- [`ErrorKind::Unsupported`]
- [`Option::insert`]
- [`Ordering::is_eq`]
- [`Ordering::is_ge`]
- [`Ordering::is_gt`]
- [`Ordering::is_le`]
- [`Ordering::is_lt`]
- [`Ordering::is_ne`]
- [`OsStr::is_ascii`]
- [`OsStr::make_ascii_lowercase`]
- [`OsStr::make_ascii_uppercase`]
- [`OsStr::to_ascii_lowercase`]
- [`OsStr::to_ascii_uppercase`]
- [`Peekable::peek_mut`]
- [`Rc::decrement_strong_count`]
- [`Rc::increment_strong_count`]
- [`Vec::extend_from_within`]
- [`array::from_mut`]
- [`array::from_ref`]
- [`char::MAX`]
- [`char::REPLACEMENT_CHARACTER`]
- [`char::UNICODE_VERSION`]
- [`char::decode_utf16`]
- [`char::from_digit`]
- [`char::from_u32_unchecked`]
- [`char::from_u32`]
- [`cmp::max_by_key`]
- [`cmp::max_by`]
- [`cmp::min_by_key`]
- [`cmp::min_by`]
- [`f32::is_subnormal`]
- [`f64::is_subnormal`]

Cargo
-----------------------
- [Cargo now supports git repositories where the default `HEAD` branch is not
  "master".][cargo/9392] This also includes a switch to the version
  3 `Cargo.lock` format which can handle default branches correctly.
- [macOS targets now default to `unpacked` split-debuginfo.][cargo/9298]
- [The `authors` field is no longer included in `Cargo.toml` for new
  projects.][cargo/9282]

Rustdoc
-----------------------
- [Added the `rustdoc::bare_urls` lint that warns when you have URLs
  without hyperlinks.][81764]

Compatibility Notes
-------------------
- [Implement token-based handling of attributes during expansion][82608]
- [`Ipv4::from_str` will now reject octal format IP addresses in addition
  to rejecting hexadecimal IP addresses.][83652] The octal format can lead
  to confusion and potential security vulnerabilities and [is no
  longer recommended][ietf6943].

Internal Only
-------------
These changes provide no direct user facing benefits, but represent significant
improvements to the internals and overall performance of rustc and
related tools.

- [Rework the `std::sys::windows::alloc` implementation.][83065]
- [rustdoc: Don't enter an infer_ctxt in get_blanket_impls for
  impls that aren't blanket impls.][82864]
- [rustdoc: Only look at blanket impls in `get_blanket_impls`][83681]
- [Rework rustdoc const type][82873]

[83386]: rust-lang/rust#83386
[82771]: rust-lang/rust#82771
[84147]: rust-lang/rust#84147
[84082]: rust-lang/rust#84082
[83799]: rust-lang/rust#83799
[83681]: rust-lang/rust#83681
[83652]: rust-lang/rust#83652
[83387]: rust-lang/rust#83387
[82873]: rust-lang/rust#82873
[82864]: rust-lang/rust#82864
[82608]: rust-lang/rust#82608
[82565]: rust-lang/rust#82565
[80525]: rust-lang/rust#80525
[79278]: rust-lang/rust#79278
[78618]: rust-lang/rust#78618
[77704]: rust-lang/rust#77704
[83941]: rust-lang/rust#83941
[83065]: rust-lang/rust#83065
[81764]: rust-lang/rust#81764
[81469]: rust-lang/rust#81469
[cargo/9298]: rust-lang/cargo#9298
[cargo/9282]: rust-lang/cargo#9282
[cargo/9392]: rust-lang/cargo#9392
[`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX
[`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER
[`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION
[`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16
[`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32
[`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked
[`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit
[`AtomicBool::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicBool.html#method.fetch_update
[`AtomicPtr::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicPtr.html#method.fetch_update
[`BTreeMap::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.retain
[`BTreeSet::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.retain
[`BufReader::seek_relative`]: https://doc.rust-lang.org/std/io/struct.BufReader.html#method.seek_relative
[`DebugStruct::non_exhaustive`]: https://doc.rust-lang.org/std/fmt/struct.DebugStruct.html#method.finish_non_exhaustive
[`Duration::MAX`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.MAX
[`Duration::ZERO`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.ZERO
[`Duration::is_zero`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.is_zero
[`Duration::saturating_add`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_add
[`Duration::saturating_mul`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_mul
[`Duration::saturating_sub`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_sub
[`ErrorKind::Unsupported`]: https://doc.rust-lang.org/std/io/enum.ErrorKind.html#variant.Unsupported
[`Option::insert`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.insert
[`Ordering::is_eq`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_eq
[`Ordering::is_ge`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ge
[`Ordering::is_gt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_gt
[`Ordering::is_le`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_le
[`Ordering::is_lt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_lt
[`Ordering::is_ne`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ne
[`OsStr::eq_ignore_ascii_case`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.eq_ignore_ascii_case
[`OsStr::is_ascii`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.is_ascii
[`OsStr::make_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_lowercase
[`OsStr::make_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_uppercase
[`OsStr::to_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_lowercase
[`OsStr::to_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_uppercase
[`Peekable::peek_mut`]: https://doc.rust-lang.org/std/iter/struct.Peekable.html#method.peek_mut
[`Rc::decrement_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count
[`Rc::increment_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count
[`Vec::extend_from_within`]: https://doc.rust-lang.org/beta/std/vec/struct.Vec.html#method.extend_from_within
[`array::from_mut`]: https://doc.rust-lang.org/beta/std/array/fn.from_mut.html
[`array::from_ref`]: https://doc.rust-lang.org/beta/std/array/fn.from_ref.html
[`cmp::max_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by_key.html
[`cmp::max_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by.html
[`cmp::min_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by_key.html
[`cmp::min_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by.html
[`f32::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal
[`f64::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal
[ietf6943]: https://datatracker.ietf.org/doc/html/rfc6943#section-3.1.1

…, r=estebank

Upgrade array_into_iter lint to include Deref-to-array types.

Fixes rust-lang#88099

Fixes the issue mentioned here: rust-lang#84147 (comment)