Initialize accessibility support on clutter_init

Initialize the accessibility support calling cally_accessibility_init

Take into account that this is required to at least be sure that
CallyUtil class is available.

It also modifies cally_accessibility_module_init in order to return
if the initialization was fine (and the name, removing the module word).

It also removes the gnome accessibility hooks, as it is not anymore
module code.

Solves CB#2098

clutter/clutter-main.h

@@ -102,6 +102,7 @@ void             clutter_do_event                   (ClutterEvent *event);
 gboolean         clutter_get_debug_enabled          (void);
 gboolean         clutter_get_show_fps               (void);
 gulong           clutter_get_timestamp              (void);
+gboolean         clutter_get_accessibility_enabled  (void);
 
 /* Threading functions */
 void             clutter_threads_init                  (void);