wn_delrow -- delete row from window

        USAGE

          wn_delrow(wn, row)
          WINDOWPTR wn;
          int row;

                wn -  window handle
                row - row at which a line is to be deleted

          Row is relative to the origin of the window.  All lines below
          the row specified are scrolled up. The currently defined window
          attribute is used to clear the lines inserted.

        RETURNS

          TRUE or NULL if error

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