Core of the changes for returning smb_uid's. smb_uid's are now

Core of the changes for returning smb_uid's. smb_uid's are now
returned as an index plus offset into the valudated_users table.
The offset (100) is added so that an smb_uid of zero becomes
an invalid value. All access into the validated_users table are
done by removing the offset and indexing into the table. Out of
ranges return NULL. Causes accesses into the validated_users table
to be more consistant and controlled.

This change made due to the fact that the uid field is only 16
bits in the smb header and we need for this not to be a unix
user id (which can ge 32 bits).

jra@cygnus.com
(This used to be commit ac265eff85a043e139b259e400fbbc444a94c97c)