Add hyperv manual pages provided by Microsoft, formatted
for FreeBSD standards.  Very little, if any, content was
modified.

These are not yet linked to the build.

Submitted by:	Abhishek Gupta (abgupta!microsoft dot com)
Sponsored by:	The FreeBSD Foundation
Connect the hyperv drivers to the build.

MFC after:	5 days
X-MFC-With:	r263105
Sponsored by:	The FreeBSD Foundation