{  The purpose of this request is to set a system flag in the XCB
{  (execution control block) of the specified task.
{
{  TYPE
{    TMT$RB_SET_SYSTEM_FLAG = RECORD
{      REQCODE,
{      STATUS,
{      TASK_ID,
{      FLAG_ID,
{    recend;
{
{  reqcode: (input) The value of this parameter is SYC$RC_MTR_SET_SYSTEM_FLAG.
{
{  task_id: (input) This parameter is the global task id of the task in
{          which the system flag is set.
{
{  flag_id: (input) This parameter specifies which system flag is to be set.
{
{  status: (output) This parameter is the standard monitor status.
