Make sure that ref and changed bits propagate back to the VM layer whenever pages are unmapped. The old code had several races that could allow these to become stale.
Make sure that ref and changed bits propagate back to the VM layer
whenever pages are unmapped. The old code had several races that could
allow these to become stale.

Approved by:	re (kib)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase