godoc: enable visibility of element linked from URL hash
godoc: enable visibility of element linked from URL hash

Expands the example when visiting a URL such as
http://golang.org/pkg/net/http/#example_Hijacker

Fixes issue 5212.

R=golang-dev, bradfitz, adg
CC=golang-dev
https://codereview.appspot.com/8378043

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,dsriram/golang,tv42/old-go,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,apparentlymart/golang,tv42/old-go,tv42/old-go,dsriram/golang,apparentlymart/golang,apparentlymart/golang,gnanderson/go,dsriram/golang,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,gnanderson/go,gnanderson/go