rem: return -1;
add: return 0;
context: TC_BUILTIN(const char *chain, const TC_HANDLE_T handle){	struct chain_head *c;		iptc_fn = TC_BUILTIN;	c = iptcc_find_label(chain, handle);	if (!c) {		errno = ENOENT;		return -1;	}	return iptcc_is_builtin(c);}