Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r271493,271688-271689,271696,271854,272139-272143:

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.

Approved by: re (gjb)

Properly revert r272128.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Revert r272149, which introduces obscure vestiges from the
r272128 reversal.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Revert r272128:
Though this passes the buildworld test, this fails during
installworld with:

make[3]: "/releng/scripts-release/chroots/10/i386/release/etc/devd/Makefile"
line 13: Malformed conditional (${MK_HYPERV} != "no")

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r271493,271688,271689,271696,271854:

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.

Approved by: re (gjb)

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Import Hyper-V paravirtualized drivers from projects/hyperv
branch into head.

Approved by: re@ (hrs)
Obtained from: Microsoft, NetApp, and Citrix.

Revert the kvp code - there's still some work that
needs to be done for that.

Discussed with: Microsoft hyper-v devs

Latest update from Microsoft.

Obtained from: Microsoft Hyper-v dev team