Inject #UD into the guest when it executes either 'MONITOR' or 'MWAIT'.

The hypervisor hides the MONITOR/MWAIT capability by unconditionally setting
CPUID.01H:ECX[3] to 0 so the guest should not expect these instructions to
be present anyways.

Discussed with:	grehan


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272670 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f