variant of the CG4 (the one with the AMD colormap DACs). This has
been tested only on the "Type B" H/W at this point (Brooktree DACs).
Thanks to Ezra Story and Scott Ellis for the "Type A" support.
- 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.
