Remove fallback to per-group lookup when matching groups in sudoers.

Remove fallback to per-group lookup when matching groups in sudoers.
The sudo front-end will now use getgrouplist() to get the user's
list of groups if getgroups() fails or returns zero groups so we
always have a list of the user's groups.  For systems with
mbr_check_membership() which support more that NGROUPS_MAX groups
(Mac OS X), skip the call to getgroups() and use getgrouplist() so
we get all the groups.

--HG--
branch : 1.8