Import HyperV Key-Value Pair (KVP) driver and daemon code by Microsoft,
many thanks for their continued support of FreeBSD.
While I'm there, also implement a new build knob, WITHOUT_HYPERV to
disable building and installing of the HyperV utilities when necessary.
The HyperV utilities are only built for i386 and amd64 targets.
This is a stable/10 candidate for inclusion with 10.1-RELEASE.
Submitted by: Wei Hu <weh microsoft com>
MFC after: 1 week