So, the mod/ref emulation in the SH3 pmap is pretty much horribly
broken :-)

BUT!  I fixed it!  At least for the mod attribute.  I pay a little
lip-service to the referenced attribute, but it could be improved.

If we improve it, let's just please re-write the pmap module.  I've
started this effort, and I can probably bang it out in a couple of
weeks, given enough spare time in the evenings.

Anyway, with fixed pmap, I can now boot multi-user on my Dreamcast
using an NFS root file system.  Yay!

I'm committing the pmap fixes now.

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>