utmpx - Bring in utmpx,wtmpx and lastlogx support

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