{
{    The purpose of this request is to add a prefix to a message.
{
{   NOTE:  If the message identifier is invalid, prefix is NIL, or prefix
{         length is zero, a system error ('Buffer Manager Caller') will occur.
{
{       NLP$BM_ADD_MESSAGE_PREFIX (PREFIX, PREFIX_LENGTH, MESSAGE_ID)
{
{ PREFIX: (input)  This parameter specifies the address of the prefix to be
{       added to the message.
{
{ PREFIX_LENGTH: (input)  This parameter specifies the length of the prefix to
{       be added to the message.
{
{ MESSAGE_ID: (input, output)  This parameter specifies the identifier of the
{       message to which the prefix is added.
{
