testing: in example, empty output not distinguished from missing output

Fixes issue 4485.

R=golang-dev, rsc, adg
CC=golang-dev
https://codereview.appspot.com/7071050

Committer: Andrew Gerrand <adg@golang.org>
text/template: Document that range can be used on chan types.

Fixes issue 4640.

R=golang-dev, adg
CC=golang-dev
https://codereview.appspot.com/7082044

Committer: Andrew Gerrand <adg@golang.org>