Add a canonical_filename value (should remain the r->filename identity)
  so we can tell if a 3rd party module broke the canonical form of the
  filename by not calling apr_filepath_merge().


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90585 13f79535-47bb-0310-9956-ffa450edef68