rem: ptr = _p->watchers;  while(ptr) { send_notify(_p, ptr); ptr = ptr->next;
add: while(watcher) { send_notify(_p, watcher); watcher = watcher->next;
context: int notify_watchers(presentity_t* _p){	struct watcher* ptr;	ptr = _p->watchers;	while(ptr) {		send_notify(_p, ptr);		ptr = ptr->next;	}	/* clear the flags */	_p->flags &= ~(PFLAG_PRESENCE_CHANGED		       |PFLAG_PRESENCE_LISTS_CHANGED		       |PFLAG_XCAP_CHANGED		       |PFLAG_LOCATION_CHANGED);	_p->flags &= ~(PFLAG_PRESENCE_LISTS_CHANGED | PFLAG_WATCHERINFO_CHANGED);	return 0;}