While implementing a tool to import lastlog entries into utmpx, I
noticed lastlogin doesn't allow custom database files to be opened. Add
a -f switch to support this. Also, add -r and -t similar to ls(1),
ruptime(1), etc. where you can sort entries by timestamp and reverse
them. This allows you to spot active/idle users more easily.
According to the manpage, the entries have to be sorted by uid. This is
no longer possible, since our utmpx implementation is completely unaware
of user IDs. You can safely add entries for multiple users sharing the
same uid.
Make the output less random by sorting everything by name.
