Currently, Meta/Cogl/Clutter makes use of cairo_rectangle_int_t despite
the existance of MetaRectangle.
In order to make MetaRectangle usable in Cogl/Clutter as well, Mtk would
provide such base types that are shared across the various private
libraries
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3128>
gtk-doc support was taken out about six years ago, but never replaced.
Add support for the newer gi-docgen, which should hopefully encourage
both C and GJS users of these libraries to improve the reference.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2248>