Removed conflict(8), because checking passwd, /var/mail, etc. is not our job.

Removed conflict(8), because checking passwd, /var/mail, etc. is not our job.
Conflict did check for:
- duplicate users
- duplicate groups
- existence of group members
- valid group ids
- orphaned maildrops
... and by the way for valid format of alias files.
The latter task can be covered by ali(1) without address arguments.
All the other tasks have nothing to do with the MUA. Actually, most of
them can be covered with shell one-liners.