code: public Content getTargetModuleLink(String target, Content label, ModuleElement mdle) {
          return getHyperLink(pathToRoot.resolve(
                  DocPaths.moduleSummary(mdle)), label, "", target);
      }
docs: Get Module link, with target frame.
  
  @param target name of the target frame
  @param label tag for the link
  @param mdle the module being documented
  @return a content for the target module link