the underlying raw device (which is expensive and causes problems).
This allows the boot program to try a sequence of names by default,
which is used to support common boot media for sun3 and sun3x.
(Now tries "netbsd.$arch" before "netbsd")
- split softc size and match/attach out from cfdriver into
a new struct cfattach.
- new "attach" directive for files.*. May specify the name of
the cfattach structure, so that devices may be easily attached
to parents with different autoconfiguration semantics.
gwr