code: public static <E> List<E> unionList(List<E> l1, List<E> l2) {
  	return new UList<E>(l1, l2);
      }
docs: Returns an immutable <code>List</code> that is the union of
  two lists: it contains first the elements from
  <code>l1</code>, and next the elements from
  <code>l2</code>.