document, in some detail with explainations and assides, how to add a
new device entry for PC Card devices with NEWCARD.

I've not connected this to the build because I can't test it locally
on this machine. Feel free to fix any problems in this file, so long
as you don't change the semantic meaning without asking me. I write
code, not docs :-)

Thanks to the person who attended my devd talk in INTEROP+NETWORLD
2003 Tokyo BSD BOF via IRC who asked me how to do this in the Q&A
section. An excellent question that I glossed over at the BOF, but
hopefully this rectifies the problem.

Eventually, I'd like to expand this to include more information about
how to write a driver for a PC Card or CardBus device, but for now
this will have to do.