A best-practice with Meson (and more generally). With Meson it's to
ensure that the right "config.h" is included when using subprojects.

REUSE way of applying licenses:
https://reuse.software/

This was done with gcu-smart-c-comment-substitution, part of
gdev-c-utils:
https://gitlab.gnome.org/swilmet/gdev-c-utils

REUSE way of applying licenses:
https://reuse.software/

This was done with gcu-multi-line-substitution, part of gdev-c-utils:
https://gitlab.gnome.org/swilmet/gdev-c-utils

To take less vertical space.

To follow more closely the REUSE way of applying licenses:
https://reuse.software/

Remove the Installation section. It should be obvious that the project
uses Meson, so people can read the Meson manual directly.

Take the latest version from GLib.

Among other changes, it adds an #include guard.

With the `checkguard` and `guard2once` utilities:
https://github.com/cgmb/guardonce

The previous commit with the guard2once command left the headers with a
trailing blank line.

Remove them with:
```
$ for i in *.h; do sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' -i $i; done
```

Recipe taken from https://www.pement.org/sed/sed1line.txt
"USEFUL ONE-LINE SCRIPTS FOR SED"

It redirects to the docs/ dir, so it's not really useful.
It was needed for the Autotools, but the project has migrated to Meson.

The goal is to have less top-level dirs.

Set `Type=session-exclusive` in all the *.test files, because I'm not
sure that the tests can run in parallel (if they add words to
dictionaries or things like that). In case of doubt, it's better to set
a setting that is known to work.

Fixes https://gitlab.gnome.org/GNOME/gspell/-/issues/37

Don't list options alphabetically. Group related options together
(gobject-introspection and vapi; tests and install_tests).

It's indeed what's documented in
https://wiki.gnome.org/Initiatives/GnomeGoals/InstalledTests

Reported-by: Jeremy Bicha

https://gitlab.gnome.org/GNOME/gspell/-/issues/37

It will be displayed by GitLab.

It is also useful for:
https://discourse.gnome.org/t/page-listing-gnome-components-like-libraries-and-bindings/22738
(for a page that lists GNOME components other than apps, using the
*.doap file and the project logo).

The logo was created with the Emblem app:
https://apps.gnome.org/en/Emblem/

The Symbolic icon is:
/usr/share/icons/Adwaita/symbolic/actions/tools-check-spelling-symbolic.svg

with a single background color, and the Square option.

Fixes "unknown type name 'NSString'" and "undefined symbols for architecture
arm64 __gspell_osx_get_preferred_spell_language" on darwin by restoring
https://gitlab.gnome.org/GNOME/gspell/-/blob/1.12.2/gspell/Makefile.am#L148-L161.

For the previous commit.

To have a shorter distance between variable definitions and use.