[misc] Update headers #endif comments

While grepping through the public headers looking for invalid use of
private HAVE_* defines, I stumbled upon two out of sync comments. Yes
it's a very minor trivial change.

clutter/clutter-actor.h

@@ -516,4 +516,4 @@ PangoLayout * clutter_actor_create_pango_layout       (ClutterActor        *self
 
 G_END_DECLS
 
-#endif /* _HAVE_CLUTTER_ACTOR_H */
+#endif /* __CLUTTER_ACTOR_H__ */

clutter/clutter-color.h

@@ -149,4 +149,4 @@ GParamSpec *clutter_param_spec_color     (const gchar        *name,
 
 G_END_DECLS
 
-#endif /* _HAVE_CLUTTER_COLOR_H */
+#endif /* __CLUTTER_COLOR_H__ */