fzap_add
int fzap_add(zap_name_t *zn, uint64_t integer_size, uint64_t num_integers,
err = fzap_add(zn, integer_size, num_integers, val, tag, tx);
err = fzap_add(zn, integer_size, num_integers, val,
err = fzap_add(zn, integer_size, num_integers, val, FTAG, tx);