Hi, People.

I've completed all of changes in pmap.c I originally intended to do.
Improvements are MIPS1 only this moment besides trivial reductions of
runtime cost.  As I don't have a R4000 DECstation, I'd like to hold
any modifications for MIPS3. 

It still have room for improvement, but its complexity and mis-guided
implementation is very fragile.  The file will be replaced anyway, by
a scratched version when PMAP_NEW w/ pool memory allocator is
completed. 

Tohru Nishimura