I've committed a reorganization of the pmax source tree.  The support
code for different baseboard models has been pulled out of machdep.c
and pmax_trap.c, and moved into new files, one for each supported
model of DECstation.

I've also reorganized some of the model-specific handling and
eliminated more of the Sprite-derived handling, in favour of code
to handle different "cpus" which is derived from the Alpha port.

(I changed the name to from "cpuconf" to "sysconf", because the mips
 port has to deal with greater differences between CPU generations,
 like mips1 vs mips3 and 32 vs 64-bit :).  If anyone realy objects,
 it can be changed back.

This looks very much like a similar reorg work done by Jason Thorpe,
and worked on and Tohru Nisimura, but I ended up redoing the
cut-and-paste level stuff myself.  I've tested on everything I could
get my hands on, with both serial and graphics consoles.  that covers
most combinatinos of motherboard, CPU daugherboard, and serial vs
graphics, except the 5000/200 with a serial console.
I plan to fold in more of Tohru's changes over the next day or so.


Next change is to revamp the bus autoconfiguration mechanism to be
compatible with the Alpha version of tc, and to move the 3100 devices
to use an autoconfig bus called "ibus" (to get them off mainbus and so
they can be shared with 5100 support.  If things go well that could
be in -current by early next week.

Simon (and the rest of you) better prepare for seeing MI device names
like sd and zs -- unless we add hooks, to override the
SunOS-compatible names in MI drivers with the names used by DEC proms.