add the given buffer indices to the given QItemSelection, both byte and char panes

def _bselect(self, selection, start_bindex, end_bindex):
        """ add the given buffer indices to the given QItemSelection, both byte and char panes """
        selection.select(self._model.index2qindexb(start_bindex), self._model.index2qindexb(end_bindex))
        selection.select(self._model.index2qindexc(start_bindex), self._model.index2qindexc(end_bindex))