o Fix OpenSSH xauth(1) command injection. [SA-16:14]
o Fix incorrect argument validation in sysarch(2). [SA-16:15]
o Fix Hyper-V KVP (Key-Value Pair) daemon indefinite sleep. [EN-16:04]

Errata: FreeBSD-EN-16:04.hyperv
Security: FreeBSD-SA-16:14.openssh-xauth, CVE-2016-3115
Security: FreeBSD-SA-16:15.sysarch, CVE-2016-1885
Approved by: so

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)

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