build: force numerical comparison in version.bash
build: force numerical comparison in version.bash

Fixes issue 2436.

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/5576075
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go