support rtl9169 on the filserver.  the imporant changes are
pc/pci.c:		recognize usrobotics for pcihinv -v; pciclrmwi from cpu kernel.
pc/etherif.c:	add "rtl8169" to recognized hardware strings.
		some extra dprints.  feel free to discard.
pc/etherdat.h:	my attempt to get rid of the #ifdef FS include block.
		delete this if you don't like the idea.
pc/ether8169.c:	driver adapted from driver submitted for cpu kernel.
the makefiles changes to */mkfile and the */io.h changes just add
ether8169.8 to the mkfile and pciclrmwi to io.h.

i am currently using this on my fs.  it's been tested under pretty good load
and seems to do well.