- switch from utmpx to utmp

There was never any difference between regular and "extended" utmp
file on linux. Some programs (like last from util-linux 2.24, or systemd)
have no knowledge about them, and keeping those files supported in PLD
is useless pain, as the whole world does not use them.
- no need for tmpfiles config, systemd owns utmp itself
- C:rc-scripts with utmpx support