FS:

FS:
	. unmap device drivers from dmap when PM signals they are dead
	. new null-io function (no_dev_io) to fill in for io functions
	  of unmapped drivers
	. driver (process number) of unmapped drivers is NONE instead of
	  0 (a valid process number)

IS:
	. print mutable flag of dmap table too

FS changes require sync() to be done 'manually' (currently by
reboot/shutdown) at shutdown time; could be caught by SIGTERM in
the future.