{
{   The purpose of this request is to combine a form to the list of forms
{ associated with a base form.  The next request that updates the screen,
{ fdp$read_forms or fdp$show_forms, replots the screen for the terminal user.
{ The form lies on top of other forms occupying the same area on the screen.
{ You cannot combine a pushed form.
{
{       FDP$COMBINE_FORM (ADDED_FORM_IDENTIFIER, COMBINE_FORM_IDENTIFIER,
{         STATUS)
{
{ ADDED_FORM_IDENTIFIER: (input)  This parameter specifies the base form.
{
{ COMBINE_FORM_IDENTIFIER: (input)  This parameter specifies the new form to
{       combine with the base form.
{
{ STATUS: (output)  This parameter specifies the name of the variable to set
{       to indicate the status of request.
{
{       condition identifiers:  fde$bad_data_value
{                               fde$form_already_added
{                               fde$form_already_combined
{                               fde$form_pushed
{                               fde$form_too_large_for_screen
{                               fde$invalid_form_identifier
{                               fde$no_space_available
{                               fde$system_error
{
