Introduce the WHPX impl

Introduce the WHPX impl

Implements the Windows Hypervisor Platform accelerator (WHPX) target. Which
acts as a hypervisor accelerator for QEMU on the Windows platform. This enables
QEMU much greater speed over the emulated x86_64 path's that are taken on
Windows today.

1. Adds support for vPartition management.
2. Adds support for vCPU management.
3. Adds support for MMIO/PortIO.
4. Registers the WHPX ACCEL_CLASS.

Signed-off-by: Justin Terry (VM) <[email protected]>
Message-Id: <1516655269[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>