{   This procedure is called to open a tape file.
{
{ NOTE:  Open positioning is not supported by this interface.  Open
{       positioning must be implemented by the caller.
{
{       BAP$TAPE_BM_OPEN(FILE_IDENTIFIER, MAXBL, STATUS)
{
{  FILE_IDENTIFIER (Input):  The file identifier for the file.
{
{  MAXBL:  (Input) The maximum block length (in bytes) to be supported for
{        this tape.
{
{  STATUS: (Output) Request status.
{
