API issues
	+ need a dispose on the bonobo_listener

UI stuff - need a CORBA_Object bonobo_widget_query_interface () method.
publicize bonobo_socket_add_id.

	+ hide / deprecate BonoboUINode
	+ create & use bonobo_ui_engine_peek_attr

	+ Add a 'register_all_these_factories' method - so we
	  can avoid nasty race conditions.