* clutter/x11/clutter-backend-x11.c (clutter_backend_x11_dispose):
Call g_slist_foreach instead of iterating over the stage_manager
list manually when deleting stages. Otherwise the 'next' pointer
of the list node can get corrupted when the actor removes itself
from the list.
* clutter/clutter-stage.c (clutter_stage_dispose): Call
clutter_actor_unrealize in the dispose handler. This fixes
problems where the dispose handler for the ClutterStageWrapper
can't deselect the GL context until the stage is unrealized.