{
{    The purpose of this request is to return the length (in bytes) of a
{ message.
{
{    NOTE:  If the message identifier is invalid, a system error ('Buffer
{          Manager Caller') will occur.
{
{       NLP$BM_GET_MESSAGE_LENGTH (MESSAGE_ID, MESSAGE_LENGTH)
{
{ MESSAGE_ID: (input)  This parameter specifies the identifier of the message
{       whose length is to be returned.
{
{ MESSAGE_LENGTH: (output)  This parameter specifies the length of the message.
{
