{   This procedure is called to force all unwritten data tape data out onto
{ the physical tape.
{
{   If no data exists which has not been written to tape this interface takes
{ no action and returns normal status.
{
{       BAP$TAPE_BM_FLUSH (FILE_IDENTIFIER, FAILURE_MODES, STATUS)
{
{  FILE_IDENTIFIER:  (Input) The file_identifier for the instance of open to
{        be flushed.
{
{  FAILURE_MODES:  (Output) Detailed information on any tape I/O error.
{
{  STATUS: (output) Request status.
