[animation] Add an emitter for ::completed

The ::completed signal requires an emitter in case we want to stop
the animation and safely dispose it inside application code without
breaking invariants.

clutter/clutter-animation.c

@@ -1133,6 +1133,24 @@ clutter_animation_get_alpha (ClutterAnimation *animation)
   return animation->priv->alpha;
 }
 
+/**
+ * clutter_animation_completed:
+ * @animation: a #ClutterAnimation
+ *
+ * Emits the ::completed signal on @animation. After this function
+ * terminates @animation will be unreferenced and it will not be
+ * valid anymore, unless g_object_ref() was called before
+ *
+ * Since: 1.0
+ */
+void
+clutter_animation_completed (ClutterAnimation *animation)
+{
+  g_return_if_fail (CLUTTER_IS_ANIMATION (animation));
+
+  g_signal_emit (animation, animation_signals[COMPLETED], 0);
+}
+
 /*
  * starts the timeline
  */

clutter/clutter-animation.h

@@ -128,6 +128,7 @@ void                 clutter_animation_unbind_property (ClutterAnimation     *an
                                                         const gchar          *property_name);
 ClutterInterval     *clutter_animation_get_interval    (ClutterAnimation     *animation,
                                                         const gchar          *property_name);
+void                 clutter_animation_completed       (ClutterAnimation     *animation);
 
 ClutterAnimation *   clutter_actor_animate               (ClutterActor         *actor,
                                                           gulong                mode,