Start to disentangle the isa attachments from other buses. Partially

Start to disentangle the isa attachments from other buses.  Partially
rewrite the pccard attachment case.  This is a work in progress, but
doesn't break the isa case.

I left the #if 0...#endif around the pccard stuff, at Peter's request,
so that normal users don't shoot themselves in the foot.

While I was here:
	o Indent a comment to the right location
	o Spell Unknown with a final 'n'.

Reviewed by: peter