Move xntpd -> rc.securelevel since tickadj need to twiddle /dev/mem

Move xntpd -> rc.securelevel since tickadj need to twiddle /dev/mem
Move xdm back to rc.local; if your X server need access to /dev/mem
    and you do not use the ap driver starting xdm from rc.securelevel
    will only help the first time.
Add other rc.securelevel examples that are not daemons.