Read/write the WakeUp time from/to the BIOS

 nvram-wakeup can read and write the wake up time in the BIOS
 (via /dev/nvram on recent 2.4.x kernels or direct I/O port access).
 On this wake up time the computer will be powered on automatically from
 the soft-off state. For the video disc recorder VDR, nvram-wakeup installs
 a hook script, that allows VDR to set a wake up time, when it powers down.