ntsync(9)

Hello,
since the recent hype around ntsync driver for Linux, written no less than
'Linux incorporates Windows features', I decided that FreeBSD should
support the trend. Useful technical summary is available at
https://fedoraproject.org/wiki/Changes/NTSYNC-Contained

Apparently, there is some documentation 
https://docs.kernel.org/userspace-api/ntsync.html
(which mis-spells ioctl names), and the test suite that seems to be
more useful.

FreeBSD port of the test suite can be found at
https://github.com/kostikbel/freebsd-ntsync-test
and the FreeBSD driver implementation at
https://reviews.freebsd.org/D57038

This is a clean-room implementation, I did not read GPL-ed code.
I used the documentation as reference, and ensured that the test suite
passes fully.  Amusingly, there was one test that contained bug in
the check.