* clutter/clutter-actor.[ch]: Remove the ::event-after signal
class handler, as it's not meant to be overridden by sub-classes.
(clutter_actor_class_init):
Make every event-related signal return a boolean: return TRUE
in a signal handler to block the emission. The value is accumulated
automatically by the signal API.
(clutter_actor_event): If ::event returns TRUE, skip to emitting
::event-after. Return the value accumulated by the signal emission
chain.
* clutter/clutter-private.h: Rename _clutter_boolean_accumlator().
* clutter/clutter-main.c (clutter_do_event): If clutter_actor_event()
returns TRUE then stop the event emission chain from child to parent.
* clutter/clutter-stage.c (clutter_stage_event): Behave like
clutter_actor_event().
(clutter_stage_get_key_focus),
(clutter_stage_set_key_focus): Avoid a nasty circular reference
issue: if the actor passed to set_key_focus is NULL then the stage
has the key focus.
* tests/test-events.c: Update the events test with the API
changes.