misc/dist: trim space from version string
misc/dist: trim space from version string

This prevents us from writing filenames like "weekly.2012-03-12\n.foo.bar.tar.gz".

R=bradfitz
CC=golang-dev
http://codereview.appspot.com/5783090
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go