rem: int free_presentity(presentity_t* _p)
add: void free_presentity(presentity_t* _p)
context: int free_presentity(presentity_t* _p){	watcher_t* ptr;	while(_p->watchers) {		ptr = _p->watchers;		_p->watchers = _p->watchers->next;		free_watcher(ptr);	}		if (_p->to.s) shm_free(_p->to.s);	shm_free(_p);}