wn_clr -- clear window

        USAGE

          wn_clr(wn)
          WINDOWPTR wn;

                wn - window handle

          The window corresponding to wn is cleared (mini clear screen).
          The currently defined window attribute is used to clear the
          interior of the window.

          The windows virtual cursor is homed.

        RETURNS

          TRUE or NULL if error

        CAUTIONS

          The window "wn" automatically becomes the top window tile upon
          return.