TITLEWIN expression

   Synopsis:
      Changes the task window's title

   Notes:
      If the script is being run from within a task, this statement asks the
         task to change the title of its task window. If an expression is 
         specified, it is used as the new title. If an empty string, zero or no 
         expression at all is specified, the window is reset to use its default 
         title.

   Requires:
      If the script is not being run as a task, or if not task window is open,
         the TITLEWIN statement is ignored (and no error message is generated).
         Execution continues with the next statement.
         
   Examples:
      OPENWIN
      WRITEWIN "Hello world!"
      PAUSE 5
      TITLEWIN "I am in charge now!"
      PAUSE 5
      CLOSEWIN
