init: massive rewrite to support SYS5 inittab

init: massive rewrite to support SYS5 inittab

Need to add telinit support to it yet.

May also make sense to extend the built in getty to understand some
basic modem setting and perhaps integrate cron as an internal.

You will now need an inittab, somethng like

id:3:initdefault:
si::sysinit:/bin/sh
is:s:respawn:/bin/sh
rc::bootwait:/etc/rc
01:3:respawn:getty /dev/tty1
02:3:respawn:getty /dev/tty2
03:3:off:getty /dev/tty3

Other things to look at that fall from this are init arguments on the boot
line