* prototype and definition for pmap_activate(p). Updates the segtab,
and changes the active ASID if p == curproc.
* Make reserved fixed-address (UADDR) kernelstack PTEs global,
so we still have a kernel stack after pmap_activate() on curproc.
* make KSEG2 mappings for p_addr global (see above.)
Seems to detune contextswitch and NTP resolution (by 60 ms), but
thepmap_activate() interface is mandatory. Needs more thought.
Move mips-specific pmap definitions (PMAP_PREFER for mips3, declaratin
of pmap_bootstrap() for the system-specific machdep.c) from
arch/pmax/include/pmap.h to arch/mips/include/pmap.h.