rem: watch_node(const node_ref *node, uint32 flags, BMessenger target)
add: watch_node(const node_ref *node, uint32 flags, const BHandler *handler, const BLooper *looper)
context: watch_node(const node_ref *node, uint32 flags, BMessenger target){	status_t error = (target.IsValid() ? B_OK : B_BAD_VALUE);	if (error == B_OK) {		BLooper *looper = NULL;		BHandler *handler = target.Target(&looper);		error = watch_node(node, flags, handler, looper);	}	return error;}