This CL updates CL 7511043;
- adds new test cases for both UDPConn and UnixConn,
- makes sure unnamed UnixAddr handling,
- replaces t.Errorf with t.Fatalf in sockname related test cases.
Fixes#3721 (again).
Fixes#3838 (again).
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7627048
Handle return values from recvfrom correctly when the
kernel decides to not return an address.
Fixes#4636.
Fixes#4352.
R=rsc, mikioh.mikioh, dave
CC=golang-dev
https://golang.org/cl/7058062