This reverts commit 16d49695ad.
If we want an actor to go away deterministically, we should call
clutter_actor_destroy(); using unparent instead a) may result
leaks through cyclic ref counts, and b) will delay the deallocation
of the window texture in a garbage collected environment until
the next garbage collection, causing much greater transient use
of memory.
http://bugzilla.gnome.org/show_bug.cgi?id=580520
072ec184d3
