* cpuregs.h:
Delete unused VMMACH_ names (e.g., duplicates of PTE bits in pte.h).
Change remaining VMMACH_xxx names to MIPS1_xxx or MIPS3_xx.
Fold remaining compile-time definitions into a single #ifdef MIPS3.
* Use MIPS1_ names in locore_r2000.S, mips3_ names in locore_r4000.S
* Garbage-collect MachHitFlushDCache()
* psl.h:
use MIPS1_, MIPS3_ symbolic names for Cause register bits.
change _R3K to MIPS1_, _R4K to MIPS3. Conditionalize for mips1 only,
mips3 only, or when both are defined, use runtime CPUISMIPS3 test.
Change pmax/include/psl.h to just do #include <mips/psl.h>.
pmax/include/psl.h would go away completely if it wasn't stil required
by compat/common/kern_exit_43.c.
jonathan