illumos gate

Currently, if a uid/gid is unknown to the system, zfs(1M) would say nothing on the unknown user/group. For instance, after a user which owns uid=1002 is removed, we would have something like this, if 'destroy' is previously granted:

$ zfs allow zeta/test                   
---- Permissions on zeta/test ----------------------------------------
Local+Descendent permissions:
    user  destroy

With the attached patch applied, it would become:

$ zfs allow zeta/test                   
---- Permissions on zeta/test ----------------------------------------
Local+Descendent permissions:
    user (unknown: 1002) destroy

The proposed patch also allows 'allow' and 'unallow' to accept numerical IDs, even when they are not known to the system, when -u or -g is explicitly specified. Without the change there would be no way other than recreating a user/group that occupies the same UID/GID to revoke a granted permission to unknown user.