function addEngine(name,ext,lang,cat) {
  if ((typeof window.sidebar == "object") && (typeof window.sidebar.addSearchEngine == "function")) {
    window.sidebar.addSearchEngine(
      "http://wiki.lumrix.net/"+lang+"/plugins/"+name+".xml",
      "http://wiki.lumrix.net/"+lang+"/plugins/"+name+"."+ext,
      name,
      cat );
  }
}