The order and way include macros were structured was chaotic, with no
real common thread between files. Try to tidy up the mess with some
common scheme, to make things look less messy.
Move all objects and functions namespaced with Mutter into the Meta namespace
to get a single consistent namespace. Changes that aren't simply changing mutter
to meta:
MutterWindow => MetaWindowActor
mutter_get_windows => meta_get_window_actors
mutter_plugin_get_windows => meta_plugin_get_window_actors
https://bugzilla.gnome.org/show_bug.cgi?id=628520
