net: use original raddr if getpeername fails

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 issue 3721 (again).
Fixes issue 3838 (again).

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/7627048
doc/go1.1.html: performance
An overview is all that's required.

R=golang-dev, remyoudompheng, bradfitz, adg
CC=golang-dev
https://codereview.appspot.com/7577050
misc/kate: fix multiline raw string syntax highlighting error.
From VisualFC.
Fixes issue 4862.

R=golang-dev, minux.ma, r
CC=golang-dev
https://codereview.appspot.com/7568043

Committer: Rob Pike <r@golang.org>
cmd/5l, cmd/6l, cmd/8l: remove declaration on non-existent variables.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7985043
build: increase timeout for ARM
in an effort to make builder freebsd-arm-pi and netbsd-arm-qemu pass again.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7621050
cmd/cc: fix typo leading to index out of range.

Detected by GCC static analysis.

Fixes issue 5117.

R=golang-dev, ality, minux.ma
CC=golang-dev
https://codereview.appspot.com/7665047