Implementing API to link sysctl nodes to devices.

[KILOREUX Emperex]

Status update for this week:

After a deep discussion about the design for the new API (which took a
little bit longer than planned), and for me to investigate the community
feedback (Discussion here :
https://lists.freebsd.org/pipermail/freebsd-arch/2016-June/017817.html) , I
have started the implementation of the API inside the kernel, I am a bit
late behind schedule due to unpredicted circumstances, but will be working
18 hours a days for the next week to catch up, I started the implementation
of the API inside the kernel yesterday, so breking it down:
* Initial API design: done
* Implementation : Working on it