quite work yet, so the heart of it is disabled.
Added bdev and cdev args to dsopen().
drivers:
Fixed device names, links, minor numbers and modes.
wd.c:
Started actually supporting devfs.
diskslice.h:
Added devfs tokens to structs (currently 576 of them per disk! :-().
subr_diskslice.c:
Create devfs entries in dsopen() and (unsuccessfully) attempt to make
them go away at the right times. DEVFS is #undefed at the start so
that this shouldn't cause problems.