Kurobox/T4 power management added

["Toru Nishimura" <locore64%alkyltechnology.com@localhost>]

Hi,

I added KuroBox/T4 power management stuff to satmgr(4).

- reboot(8),
- poweroff(8),
- a long (over 3-second) press on front panel PWR button.

I expect the above are now functional, however, has no luck to test
them with a real HW so far.  It'd be a help when anyone reports me
back about how the new code works.

Toru Nishimura / ALKYL Technology