{
{   The purpose of this request is to allow an application to register a
{ procedure with MLI which will be invoked whenever another application
{ performs an mlp$send_message or mlp$receive_message request specifying
{ that a signal is to be sent.
{
{        MLP$REGISTER_SIGNAL_HANDLER (APPLICATION_NAME, HANDLER, STATUS)
{
{ APPLICATION_NAME: (input) This parameter specifies the application
{        name by which the calling program identifies itself to MLI and
{        other applications.
{
{ HANDLER: (input) This parameter specifies a pointer to procedure which
{        will be invoked (called) whenever an mlp$send_message or
{        mlp$receive_message request causes a signal to be sent to this
{        application.
{
{ STATUS: (output) This parameter specifies the request status.
{        The following status values may be returned by this request:
{           mlc$busy_interlock
{           mlc$receiver_name_syntax_error
{           mlc$receiver_not_signed_on
{           mlc$system_name_no_match
{
