Avoid populating *_VERSION constants through cflags in pkg-config-file
which could be overridden by the project using it. Properly prefix the
defines with META_ to make gi-scanner happy.
Modify all visible instances of mutter with mutter-wayland
(libraries, folders, pkgconfig, etc.), so that the wayland
branch can be installed alongside the usual X11 mutter.
https://bugzilla.gnome.org/show_bug.cgi?id=705497
Move preferences to GSettings, using mainly shared schemas from
gsettings-desktop-schemas.
Unlike GConf, GSettings support is not optional, as Gio is already
a hard dependency of GTK+.
https://bugzilla.gnome.org/show_bug.cgi?id=635378
