sort: use proper mass unit in example

The values for the planet masses are given in
earth mass, not solar mass.

R=golang-dev, dave, r
CC=golang-dev
https://codereview.appspot.com/7368054

Committer: Rob Pike <r@golang.org>
cmd/gc: don't emit type instructions for nonexisting locals

If all locals are optimized away, the type instructions would stay in the instruction stream. Call fixautoused to scrub the output.

Fixes issue 4915.

R=rsc
CC=golang-dev
https://codereview.appspot.com/7385055