It cuts away a bit of the GObject boilerplate, gives us support for `g_autoptr`, and removes the typedef hack inside clutter-master-clock.c. https://gitlab.gnome.org/GNOME/mutter/merge_requests/380
In cogl use cogl-config.h and in clutter use clutter-build-config.h. We can't use clutter-config.h in clutter because its already used and installed. https://bugzilla.gnome.org/show_bug.cgi?id=768976
