ted.library/TEDGetFilename
   NAME
       TEDGetFilename -- return the name of file currently loaded

   SYNOPSIS
       filename = TEDGetFilename()
       D0

   FUNCTION
       Get SuperTED to return a string holding the name of the current file

   RESULTS
       filename  -- a pointer to a null terminated string holding the
                    full path to the currnt file

   NOTES
       The pathname is taken from the 'directory' string in the Load
       requester - so it may well be blank.