[DO NOT MERGE] NLL crater run 3: deny NLL warnings in migrate mode

Forward port of #60914.

r? @ghost

cc @rust-lang/lang
cc @rust-lang/wg-compiler-nll

…tthewjasper

Rust 2018: NLL migrate mode => hard error

As per decision on a language team meeting as described in rust-lang#63565 (comment), we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.

cc @rust-lang/lang
cc @rust-lang/wg-compiler-nll

Rollup of 8 pull requests

Successful merges:

 - #63565 (Rust 2018: NLL migrate mode => hard error)
 - #63969 (Add missing examples for Option type)
 - #64067 (Remove no-prefer-dynamic from valgrind tests)
 - #64166 (Better way of conditioning the sanitizer builds)
 - #64189 (annotate-snippet emitter: Deal with multispans from macros, too)
 - #64202 (Fixed grammar/style in some error messages)
 - #64206 (annotate-snippet emitter: Update an issue number)
 - #64208 (it's more pythonic to use 'is not None' in python files)

Failed merges:

r? @ghost

…hewjasper

 Rust 2015: No longer downgrade NLL errors

As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.

The remaining work to throw out AST borrowck and adjust some tests still remains after this PR.

Fixes rust-lang#38899
Fixes rust-lang#53432
Fixes rust-lang#45157
Fixes rust-lang#31567
Fixes rust-lang#27868
Fixes rust-lang#47366

r? @matthewjasper

…hewjasper

 Rust 2015: No longer downgrade NLL errors

As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.

The remaining work to throw out AST borrowck and adjust some tests still remains after this PR.

Fixes rust-lang#38899
Fixes rust-lang#53432
Fixes rust-lang#45157
Fixes rust-lang#31567
Fixes rust-lang#27868
Fixes rust-lang#47366

r? @matthewjasper

…hewjasper

 Rust 2015: No longer downgrade NLL errors

As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.

The remaining work to throw out AST borrowck and adjust some tests still remains after this PR.

Fixes rust-lang#38899
Fixes rust-lang#53432
Fixes rust-lang#45157
Fixes rust-lang#31567
Fixes rust-lang#27868
Fixes rust-lang#47366

r? @matthewjasper

…hewjasper

 Rust 2015: No longer downgrade NLL errors

As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.

The remaining work to throw out AST borrowck and adjust some tests still remains after this PR.

Fixes rust-lang#38899
Fixes rust-lang#53432
Fixes rust-lang#45157
Fixes rust-lang#31567
Fixes rust-lang#27868
Fixes rust-lang#47366

r? @matthewjasper

Pkgsrc changes:
 * Remove patch which no longer applies (but what about RPATH?)
 * Adapt a few patches to changed files upstream.

Upstream changes:

Version 1.39.0 (2019-11-07)
===========================

Language
--------
- [You can now create `async` functions and blocks with `async fn`,
  `async move {}`, and `async {}` respectively, and you can now call
  `.await` on async expressions.][63209]
- [You can now use certain attributes on function, closure, and function
  pointer parameters.][64010] These attributes include `cfg`, `cfg_attr`,
  `allow`, `warn`, `deny`, `forbid` as well as inert helper attributes used
  by procedural macro attributes applied to items. e.g.
  ```rust
  fn len(
      #[cfg(windows)] slice: &[u16],
      #[cfg(not(windows))] slice: &[u8],
  ) -> usize {
      slice.len()
  }
  ```
- [You can now take shared references to bind-by-move patterns in the
  `if` guards of `match` arms.][63118] e.g.
  ```rust
  fn main() {
      let array: Box<[u8; 4]> = Box::new([1, 2, 3, 4]);

      match array {
          nums
  //      ---- `nums` is bound by move.
              if nums.iter().sum::<u8>() == 10
  //                 ^------ `.iter()` implicitly takes a reference to `nums`.
          => {
              drop(nums);
  //          ----------- Legal as `nums` was bound by move and so we have ownership.
          }
          _ => unreachable!(),
      }
  }
  ```

Compiler
--------
- [Added tier 3\* support for the `i686-unknown-uefi` target.][64334]
- [Added tier 3 support for the `sparc64-unknown-openbsd` target.][63595]
- [rustc will now trim code snippets in diagnostics to fit in your terminal.]
  [63402] **Note** Cargo currently doesn't use this feature. Refer to
  [cargo#7315][cargo/7315] to track this feature's progress.
- [You can now pass `--show-output` argument to test binaries to print the
  output of successful tests.][62600]

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

Libraries
---------
- [`Vec::new` and `String::new` are now `const` functions.][64028]
- [`LinkedList::new` is now a `const` function.][63684]
- [`str::len`, `[T]::len` and `str::as_bytes` are now `const` functions.][63770]
- [The `abs`, `wrapping_abs`, and `overflowing_abs` numeric functions are
  now `const`.][63786]

Stabilized APIs
---------------
- [`Pin::into_inner`]
- [`Instant::checked_duration_since`]
- [`Instant::saturating_duration_since`]

Cargo
-----
- [You can now publish git dependencies if supplied with a `version`.]
  [cargo/7237]
- [The `--all` flag has been renamed to `--workspace`.][cargo/7241] Using
  `--all` is now deprecated.

Misc
----
- [You can now pass `-Clinker` to rustdoc to control the linker used
  for compiling doctests.][63834]

Compatibility Notes
-------------------
- [Code that was previously accepted by the old borrow checker, but rejected by
  the NLL borrow checker is now a hard error in Rust 2018.][63565] This was
  previously a warning, and will also become a hard error in the Rust 2015
  edition in the 1.40.0 release.
- [`rustdoc` now requires `rustc` to be installed and in the same directory to
  run tests.][63827] This should improve performance when running a large
  amount of doctests.
- [The `try!` macro will now issue a deprecation warning.][62672] It is
  recommended to use the `?` operator instead.
- [`asinh(-0.0)` now correctly returns `-0.0`.][63698] Previously this
  returned `0.0`.

[62600]: rust-lang/rust#62600
[62672]: rust-lang/rust#62672
[63118]: rust-lang/rust#63118
[63209]: rust-lang/rust#63209
[63402]: rust-lang/rust#63402
[63565]: rust-lang/rust#63565
[63595]: rust-lang/rust#63595
[63684]: rust-lang/rust#63684
[63698]: rust-lang/rust#63698
[63770]: rust-lang/rust#63770
[63786]: rust-lang/rust#63786
[63827]: rust-lang/rust#63827
[63834]: rust-lang/rust#63834
[63927]: rust-lang/rust#63927
[63933]: rust-lang/rust#63933
[63934]: rust-lang/rust#63934
[63938]: rust-lang/rust#63938
[63940]: rust-lang/rust#63940
[63941]: rust-lang/rust#63941
[63945]: rust-lang/rust#63945
[64010]: rust-lang/rust#64010
[64028]: rust-lang/rust#64028
[64334]: rust-lang/rust#64334
[cargo/7237]: rust-lang/cargo#7237
[cargo/7241]: rust-lang/cargo#7241
[cargo/7315]: rust-lang/cargo#7315
[`Pin::into_inner`]: https://doc.rust-lang.org/std/pin/struct.Pin.html#method.into_inner
[`Instant::checked_duration_since`]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.checked_duration_since
[`Instant::saturating_duration_since`]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.saturating_duration_since