* Move mips-I pte (TLBlo) definitions from pmax/include/pte.h
to mips/include/mips1_pte.h
* Move mips-III pte (TLBlo) definitions from pica/include/pte.h
to mips/include/mips3_pte.h
* Add new mips/include/pte.h, which includes exactly one of
mips1_pte.h or mips3_pte.h (which still have namespace collisions),
depending on "options MIPS1" or "options MIPS3". (hack).
Move soft kvtopte(), ptetovk() definitions to mips/include/pte.h
* Add macro PTE_TO_PADDR() to hide the different hardware TLB formats
when mapping from pte to physical address.
* Add macro PTE_READONLY() to hide lack of SW read-only bit in mips-III
tlb. (mips1 pmap uses a sw bit in the PTE, mips3 looks up RO bit in
the kernel pmap.)
* Use macros (not direct TLB frobbing) in mips/trap.c, to make it
mips-1/mips-III indepenndet.
* Change {pmax,pica}/include/pte.h to just do #include <mips/pte.h>.