New vendor branch for FreeBSD on Hyper-V. Please review.

[Larry Melia]

We are currently preparing our “enlightened” device drivers for inclusion
with the standard distribution of FreeBSD. They provide significant
performance enhancements to FreeBSD on Hyper-V. As part of this process we
are making our source code available for review by the FreeBSD community.
 We would truly appreciate your comments and concerns.

There are two options for enabling the drivers. You can include them as a
monolithic build (
https://github.com/FreeBSDonHyper-V/freebsd/wiki/Build-the-kernel-with-the-HyperV-drivers)
or as loadable drivers by manually configuring them to load at boot time.
So, while we plan to include them in the GENERIC build for AMD64, they are
only loaded by including them in the boot configuration.

Since we will be actively maintaining our drivers, we are placing them in a
vendor branch. However, there’s a small patch to the ATA driver that when
it detects the presence of Hyper-V it disables it. This allows our
“enlightened” storage driver to replace it and provide Fast IDE for the
file system. Furthermore, we wish that the current maintainer of the ATA
driver also maintain this patch. This will allow our focus to be on our
drivers and prevent us being a hindrance to any future changes to the ATA
driver.

Our source code can be reviewed on Github at
https://github.com/FreeBSDonHyper-V/VendorBranchForFreeBSDonHyper-V.  You
may leave comments or questions on this issue board
https://github.com/FreeBSDonHyper-V/VendorBranchForFreeBSDonHyper-V/issues.
Or if you prefer, you may post them on this mailing list (
http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization).