Stop soyutils from clobering goog.string.  This will allow apps to use uncompressed files.  A copy of this change is being submitted to the Soy team at Google.

R=tobyk100@gmail.com

Review URL: https://codereview.appspot.com/12630043

git-svn-id: http://blockly.googlecode.com/svn/trunk@1196 c400ca83-b69d-9dd7-9705-49c6b8615e23