Pull up following revision(s) (requested by thorpej in ticket #515):

sys/arch/vax/vax/pmap.c: revision 1.200

rmspace(): when a PT page is put back onto the free list, invalidate
it's VA in the TB.

rmptep(): Add a comment that the no TIBS is needed for newly-freed PT
pages here because all of the callers perform a TBIA.

(martin)