rtadvd/rtadvctl from FreeBSD

[Charles Musser]

I have been experimenting with IPv6 SLAAC, using Dfly as a
router. In particular, I wanted DNS information distributed via
router advertisements, as specified in RFC 6106. FreeBSD 10.1's
rtadvd daemon does this, so I incorporated it and its companion
utility, rtadvctl, into the DragonFly base system

This wasn't too hard. I copied the code into my local /usr/src
repo (I'm working off of DragonFly_RELEASE_4_2), updated a system
include file in netinet to define some stuff needed by the
programs and rebuilt the world.. It compiles cleanly and seems to
work, although I have not done super exhaustive testing. Would
you like the diff that incorporates it? How does the contribution
process work?

Chuck