After comparing how other systems deal with utmp/utmpx, I noticed many
systems don't even care about ttyslot(3) anymore, since utmpx doesn't
use TTY slots anyway. We don't provide any tools to access old utmp
files anymore, so there is no use in letting applications write to a
proper offset within the utmp file.
Just let ttyslot(3) always return 0, which seems to be the default
behaviour on operating systems like Linux as well.
The ttyslot() function was originally part for SUSv1, marked LEGACY in
SUSv2 and removed later on. This function only makes sense when using
utmp(5), because it was used to determine the offset of the record for
the controlling TTY. It makes little sense to keep it here, because the
new utmpx file format doesn't index based on TTY slots.
It seems ttyslot() calls rindex(), to strip the device name to the last
slash, but this is obviously invalid. /dev/pts/0 should be stripped
until pts/0. Because /etc/ttys only supports TTY names in /dev/, just
strip this piece of the pathname.
