Hi all,

With lots of help from Noriuki Soda and Torhu Nisimura, i committed
soda's sys/arch/mips changes. These add the necessary support for ARC
machines with r4000 and r4400 CPUs.  Support for r4600 and r5000 CPUs
clashes with the L2 caches on mips3 pmaxes; work is in progress on that.

A Decstation 5000/150 is running fine with the changes. I don't
anticiapte any problems.  Since -current is currently in flux with
signal-delivery changes, I dont expect anyone will try this for a day
or so; but if you do encounter problems, please send a PR.  Thanks!


The ARC code itself is not yet in the tree; it's being bootstrapped on
more ARC platforms first. (Volunteer Testers, besides the usual
suspects, welcomed!)