on tech-kern. (See man page.) Implementation by Greg Hudson.
Also, remove special case for i386 in vector handling, although this code isn't
actually used any more.
- 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.