sort: move example to package level and simplify further

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/13634044
doc/go1.2.html: compiler changes
Document the semantic changes within the gc toolchain.

Also delete the mention of unbalanced right delims in template
That change was rolled back.

Absent typos, things we've forgotten, and new things that happen,
the release notes are ready.

R=golang-dev, adg, dominik.honnef
CC=golang-dev
https://codereview.appspot.com/13368052