SendmsgN is an alternate version Sendmsg that also returns
the number of bytes transferred, instead of just the error.
Update #7645
LGTM=aram, iant
R=iant, aram, bradfitz
CC=golang-codereviews
https://golang.org/cl/81210043
Solaris doesn't have struct ip_mreqn, instead it uses struct ip_mreq
and struct group_req with struct sockaddr_storage.
Also fixes incorrect SockaddrDatalink.
Update #7399
LGTM=aram, iant
R=golang-codereviews, aram, gobot, iant
CC=golang-codereviews
https://golang.org/cl/73920043
These are only the new files, autogenerated files are in a
different CL to keep the size down.
LGTM=dave, minux.ma, jsing
R=golang-codereviews, dave, jsing, gobot, minux.ma, rsc, iant, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/36000043
