code: protected void addAllClassesLink(Content ul) {
          Content linkContent = getHyperLink(DocPaths.ALLCLASSES_FRAME,
                  allclassesLabel, "", "packageFrame");
          Content li = HtmlTree.LI(linkContent);
          ul.addContent(li);
      }
docs: Adds "All Classes" link for the top of the left-hand frame page to the
  documentation tree.
  
  @param ul the Content object to which the "All Classes" link should be added