o feature #558618: display image when generating administrative reports
      NOTICE: The ad_report module is now dependent on the chart module
      available at http://drupal.org/project/chart -- this means that all
      charts are now built using Google's Charts API.
 - ad_module.install
    o feature #558618: modify index to greatly improve reporting performance
      CAUTION: This update will take a _very_ long time to run if you have a
      large ad_statistics table, locking the table and possibly preventing ads
      from being properly displayed while the update is running.