Use Publican revision history instead of Yelp
    
    In F12, the Yelp display of Revision_History.xml did not work
    properly, so we added another file, RevHistory.xml which was formatted
    appropriately.  However, in Fedora 13, we are using HTML documents and
    displaying through the user's default browser, so this file is no
    longer needed.
    
    This commit updates Release_Notes.xml to reference
    Revision_History.xml, however, RevHistory.xml has not been removed yet
    so we don't disturb the translated builds in the period until we
    update the POTs.