clear v1.3 (two version, a+b), by van Hauser / THC
does a real deletion of the entrys, supports utmp/wtmpx of sys v systems.
modifies utmp/wtmp/lastlog/utmpx/wtmpx and sets the lastlog correct.
version a deletes ALL entrys of a user (and old zap'ed entries), version b
only the last entry.
