This CL adds missing IPv6 socket options which are required
to control IPv6 as described in RFC 3493, RFC 3542.
Update #5538
R=golang-dev, dave, iant
CC=golang-dev
https://golang.org/cl/9373046
Update #4929
Regenerated from FreeBSD-9.1 for amd64 and 386, FreeBSD-CURRENT for arm.
R=devon.odell, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/7438053