HEADS UP: matt-nb5-mips64 merge to HEAD

[Matt Thomas <matt%3am-software.com@localhost>]

I've spent the past few days merging my matt-nb5-mips64 to HEAD.

It's now in a state almost ready to commit.  This affects every mips port in a 
major way.  Several thing change (IPL/spl code, interrupts, soft interrupts, 
pmap, tlb, ...) in various major ways.  This could almost be considered a 
rewrite of the mips code.

This merge affects over 400 lines in sys/arch alone.  There is bound to be 
breakage since I can't test all platforms but I will try to fix things ASAP.

After the merge is done, a few things will still need to be done:

1) make struct disklabel 64bit clean (need compat code for the old sized 
disklabel)

2) 64-bit clean routing socket.  This makes it possible to run a system with a 
netbsd32 userland.