code: protected boolean renameTileSet (String oldName, String newName)
      {
          Integer tsid = _map.get(oldName);
          if (tsid != null) {
              _map.put(newName, tsid);
              // fudge our stored tileset ID so that we flush ourselves when
              // the rename tool requests that we commit the changes
              _storedTileSetID--;
              return true;
  
          } else {
              return false;
          }
      }
docs: Copies the ID from the old tileset to the new tileset which is
  useful when a tileset is renamed. This is called by the {@link
  RenameTileSet} utility.