Doing janitor work for tridge.

Doing janitor work for tridge.
"changed the order of checking whether a SID is a UID or a GID in posix
acls. This is needed because sid_to_uid always claims that the sid is
a user, due ot a change I made some months back.

This change was suggested by Chere Zhou, but is really an interim
measure. Chere is looking at a longer term solution."

REMEMBER - 3.0 is the one we will SHIP !

Jeremy.
(This used to be commit a4d7496994b740e074398d98c999a803afff4404)