Doxygen in a main project shall not be called before tag files have been
created or updated in subprojects.

A main project can depend on it. Doxygen in a main project shall not
be called before libstdc  .tag has been created or updated.

skeleton and glibmm can be subprojects of skeletonmm.

* meson.build:
* skeletonmm/doc/reference/meson.build:
* skeletonmm/meson.build:
* skeletonmm/skeleton/skeletonmm/meson.build:
Call add_dist_script() in a subproject, if meson.version() >= 0.58.0.
* util/build_scripts/dist-build-scripts.py:
* util/build_scripts/dist-changelog.py:
* util/build_scripts/doc-reference.py:
* util/build_scripts/generate-binding.py:
* util/meson_aux/extra-dist-cmd.py:
Use MESON_PROJECT_DIST_ROOT if it exists, else MESON_DIST_ROOT.
It exists if meson.version() >= 0.58.0.

* util/build_scripts/doc-reference.py:
* util/build_scripts/generate-binding.py:
* util/meson_aux/extra-install-cmd.py: Don't print names of installed
files or other informative messages if the environment variable
MESON_INSTALL_QUIET is set.
It is set by "meson install --quiet" in Meson 0.54.0 and newer.

util/meson_aux/extra-install-cmd.py: Ignore FileNotFoundError.
On Windows, subprocess.run() may fail to find aclocal even if
the calling meson.build file has found it. Ignore this case.

https://mail.gnome.org/archives/gtkmm-list/2021-April/msg00005.html

Add "implicit_include_directories: false" to library() and executable().
Don't use the deprecated dep.get_pkgconfig_variable() function.
Change dependencies: glibmm-2.4 -> glibmm-2.68, sigc  -2.0 -> sigc  -3.0.

If mm-common is a subproject, make mm-common-get2 that can be executed
without being installed. The main project is built before the subprojects
have been installed.

The paths to the source code in untracked/ shall be relative to the
meson.build file, when library files are built from a tarball.
With absolute paths Meson may generate too long file names.
See merge request gtkmm!61

See https://github.com/libsigcplusplus/libsigcplusplus/pull/65

This is what Meson does.

Should have been fixed when skeletonmm/tools/dist-cmd.py was removed.

The caller (a meson.build file in e.g. glibmm) can specify git-tracked
files and directories that shall not be included in the tarball.
They shall be removed from MESON_DIST_ROOT.

The DevHelp base path shall not include DESTDIR. Fixes #2

* skeletonmm/doc/reference/meson.build:
* util/doc-install.pl: Move some code from meson.build to doc-install.pl,
where regular expressions can be used.

Doxygen 1.8.16 and later does not store tag file names in the html files.

* skeletonmm/doc/reference/meson.build:
* util/doc-install.pl: Modify so that references to other modules are
still updated in the html files when they are installed.

Doxygen since version 1.8.0 does not use PERL_PATH and MSCGEN_PATH.

libdir=${exec_prefix}/lib, as when it's generated with Autotools.

* meson.build: Remove dist-cmd.py from the skeletonmm tarball.
* skeletonmm/doc/reference/meson.build:
* skeletonmm/skeleton/skeletonmm/meson.build: Don't use dist-cmd.py.
* skeletonmm/meson.build: Don't use dist-cmd.py. Add a better error message
if mm-common-get is required but not found. If not maintainer-mode, check
that generate-binding.py exists.
* skeletonmm/meson_options.txt: Default value of warnings is 'min'.
Add dist-warnings.
* skeletonmm/tools/dist-cmd.py: Removed file. It's not necessary in
add_dist_script() when the first parameter is python3.path().

util: Add script to check gmmproc version

See merge request GNOME/mm-common!5

This adds a new utility script for Meson builds to check on what gmmproc
version was used (or is to be used) to generate the sources, so that we
can know whether we are ready to use compiler directives to export
symbols by defining macros during the build of the various -mm C  
modules.

* skeletonmm/doc/reference/meson.build: Less difference between
maintainer-mode and not maintainer-mode.
* keletonmm/skeleton/skeletonmm/meson.build: Make separate lists of
built .h files and built .cc files.

Don't use perl.path() when configuring Doxyfile, if perl is not found.
Perl is not required, if build-documentation=false.
See https://github.com/libsigcplusplus/libsigcplusplus/issues/53

In a git worktree, .git is a regular file.

See MR pangomm!8

Make libstdc  .tag retrieval work for Windows

See merge request GNOME/mm-common!3

With this, the mm-common package will now build for Windows/MSVC; it
is still a long way to go to actually make it usable for Windows

This ensures that we use the curl.exe and wget.exe that we happen to
find, and the corresponding DLLs of the libraries can be loaded.

Another update from upstream:
https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html

The files in the skeletonmm directory now show the start of a project
that will use Meson.

The new skeletonmm is based on experience from building pangomm with Meson.
It does not include code necessary for running Meson under MSVC.
See !2 and pangomm!4. Fixes #1

Support modules that are built with Meson

See merge request GNOME/mm-common!2

Don't use text=True in subprocess.run(). It does not exist in Python 3.5
which is the Python version that mm-common requires.