code: private <T extends PackageDoc> void mapAnnotations(Map<String,List<T>> map, PackageDoc doc,
              T holder) {
          for (AnnotationDesc annotation : doc.annotations()) {
              AnnotationTypeDoc annotationDoc = annotation.annotationType();
              refList(map, annotationDoc).add(holder);
          }
      }
docs: Map the AnnotationType to the ProgramElementDocs that use them as
  type parameters.
  
  @param map the map the insert the information into.
  @param doc the doc whose type parameters are being checked.
  @param holder the holder that owns the type parameters.