Request #30174:  Create Listener on startup (Windows), and replace
podium with listener (Motif).

The Unix and Windows platforms differ here:

Unix:  MLWorks should start with a Listener, and the podium no longer
exists, being replaced by the Listener.  The Listener now has the
interrupt button, and it also cannot be killed, otherwise MLWorks 
exits.  In this way the modified Listener acts in the same way as the
old podium, being the main window.  Messages that were displayed in
the podium are no longer available.

Windows:  MLWorks should start off with the podium maximised as
before, but now the Listener is automatiically created and is
initially visible without the need for the user to select the Listener
menu item.  There is a difference here from Unix in that the initially
created Listener on Windows can be closed since it is not the main
window of the application (the podium is) whereas on Unix, the
Listener is permanent as the application.  There is no interrupt
button on the Listener on Windows.