godoc: sort list of "other packages"
godoc: sort list of "other packages"

Fixes issue 2786.

R=r, bradfitz
CC=golang-dev
http://codereview.appspot.com/5581050

firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang