Fix an issue with dynamic loading of diff fragments

Review Request #677 — Created Dec. 18, 2008 and submitted — Latest diff uploaded

Review Board SVN (deprecated)
After installing a new reviewboard instance, I had some trouble with viewing the details of a review request.  The dynamic loading of diff fragments was broken.  "Loading diff fragment..." never went away.  We tracked it down to a missing script.  This patch fixed it for me.
Retrieving diff fragments on this box works now, where it didn't before.