USIII support

[Marius Strobl]

FYI, HEAD now has basic support for sun4u-machines based on USIII
and beyond. If you want to give it a try there's a install image
snapshot (built with neither docs nor ports) available at:
http://people.freebsd.org/~marius/8.0-20081011-SNAP-sparc64-disc1.iso.gz
Known working machines so far are: Blade 1000, Blade 1500,
Blade 2000, Fire V210, Fire 280R and Netra 20/Netra T4 though
machines similar to these like Fire V240 probably will also
just work with all essential on-board devices being supported.
AFAICT stability is en par with that on USII-based machines
(i.e. it crashed neither during lots of compilations nor heavy
network load for me).
Caveats:
o Besides serial devices, only those supported by creator(4) are
  currently usable as console, i.e. not even machfb(4) works
  at this point (it'll trigger a RED state exception, which
  shouldn't be that hard to fix though), let alone XVR cards.
o It's not clear whether all endian-bugs in mpt(4) (such
  controllers are found on-board in f.e. Fire V440) are fixed,
  yet. It works just fine with an SAS add-on card for me though.
o There's no driver for the Sun Cassini/NS Saturn Gigabit NICs
  found on-board (again f.e. Fire V440) and as add-on cards so
  far.
o There's no driver for controlling the fans in machines based
  on the Excalibur board, yet. This means that Blade 1000/2000
  aren't very useable as workstations so far due to the noise
  caused by the fans permanently running at full speed.
o There's no support for host-to-PCI-Express or host-to-PCI-X
  bridges so far due to lack of access to such machines (adding
  support for the XMITS PCI-X bridges to the existing schizo(4)
  should be rather straightforward, PCI-Express will require
  a new driver and probably some additional tweaking though).

Marius