fnvlist_merge
fnvlist_merge(*oxprops, voprops);
fnvlist_merge(origprops, zhp->zfs_props);
fnvlist_merge(origprops, zhp->zfs_user_props);
fnvlist_merge((nvlist_t *)attr, hist_nvl);
fnvlist_merge(bootenv, config);
void fnvlist_merge(nvlist_t *, nvlist_t *);