This patch implements a cleaned up hypervisor layer, plus cleans up some
of the aspects of both Hank's MS-HyperV patch and the existing VMware
driver.  In particular, the MS-HyperV information is private
information, per system, not per CPU, and can thus simply be stored in
an ordinary global variable.  This also turns the hypervisor detection
into an information structure instead of just an identifier.

	-hpa