godoc: display synopses for all packages that have some kind of documentation.
godoc: display synopses for all packages that have some kind of documentation.

Fixes issue 953.

R=rsc
CC=golang-dev
http://codereview.appspot.com/1862046
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go