This fixes bsdcpio's -R option to accept numeric
user or group Ids as well as user or group names.
In particular, this fixes freesbie2, which uses
-R 0:0 to copy a bunch of files so that the result
will be owned by root.

Also fixes a related bug that mixed-up the uid
and gid specified by -R when in passthrough mode.

Thanks to Dominique Goncalves for reporting this
regression.

Approved by: re (kib)