Sync utmp_update(8) with NetBSD.

Not much to see here.

utmpx - Bring in utmpx,wtmpx and lastlogx support

* This commit introduces the necessary support for utmpx, wtmpx and
lastlogx, as well as updating many base utils to work with these
while mostl

utmpx - Bring in utmpx,wtmpx and lastlogx support

* This commit introduces the necessary support for utmpx, wtmpx and
lastlogx, as well as updating many base utils to work with these
while mostly maintaining compatibility with the old utmp, wtmp and
lastlog.

* The new last(1) supports wtmpx but defaults to wtmp as not all wtmp
writers have been updated for wtmpx.

* All utmp readers support both utmp and utmpx now.

* lastlogin (the only lastlog reader) supports both lastlog and
lastlogx.

* The utils who(1) and finger have been almost directly replaced by
their NetBSD equivalent. In case of who(1) the only custom
modification is the behaviour of '-b' to be as it has always been.

* Partially-Obtained-from: NetBSD

show more ...