code: protected boolean setVisited(PRIndirectReference ref) {
          IntHashtable refs = (IntHashtable)visited.get(ref.getReader());
          if (refs != null)
          	return (refs.put(ref.getNumber(), 1) != 0);
          else
          	return false;
      }
docs: Sets a reference to "visited" in the copy process.
  @param	ref	the reference that needs to be set to "visited"
  @return	true if the reference was set to visited