Inject #UD into the guest when it executes either 'MONITOR' or 'MWAIT' on
an AMD/SVM host.

MFC after:	1 week
Add arm option ARM_NEW_PMAP, to allow us to begin adding the new pmap
code alongside the existing implementation and quickly toggle between
the two implementations when testing.  Once the new code is past its
teething stage we can remove this option.
Add armv6 implementations of these cache operations to avoid duplicating
the #ifdef stuff at multiple points the functions are called from.  Also
rework the armv7 implementations so that the invalidate operations work
from outermost to innermost cache level, and the writeback works from
inner to outer levels.
Export MAXCPU to the assembler code, needing by upcoming changes to locore.S.