Resolve the list of gids passed in from the sudo frontend (the

result of getgroups()) to names and store both the group names and
ids in the sudo_user struct.  When matching groups in the sudoers
file, match based on the names in the groups list first and
only do a gid-based match when we absolutely have to.  By matching
on the group name (as it is listed in sudoers) instead of id
(which we would have to resolve) we save a lot of group lookups
for sudoers files with a lot of groups in them.

--HG--
branch : 1.8