Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Drop <bsd.man.mk> support from <bsd.kmod.mk>.

Not objected to by: -current

Add a Makefile for the sample node so It can be compiled.
This helps to stop it from geting out of sync.
It is not part of the normal build but I can use it with all the others
when I make changes to netgraph to ensure it is buildable.