- 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.
keep going.
Improve error messages to include device name.
use STATIC for function declarations/definitions so it's easier to get a
useful symbol table by flipping a switch.
jtk