wn_exit -- exit window system

        USAGE

          wn_exit()
          wn_init() and wn_exit(), if used, should be the first and last
          functions called. wn_init() saves the video state and
          application entry screen.  wn_init() is typically the very
          first function called in the main program. wn_exit() restores
          the saved video state and screen image.  wn_exit() is typically
          called just prior to calling exit().

        RETURNS

          TRUE if successful, FALSE if error.

        CAUTIONS

          NONE.