PieSlice procedure

  DECLARATION:  PieSlice(X, Y : Integer; StAngle, EndAngle,
                         Radius : Word);

      PURPOSE:  Draws and fills a pie slice.

         UNIT:  Graph

      REMARKS:  This draws a pie slice, using (X,Y) as the center
                point, and drawing from StAngle to EndAngle.  The pie slice
                is outlined in the current color and filled using the pattern
                and color set by SetFillStyle or SetFillPattern.

                Errors are returned through GraphResult.

 RESTRICTIONS:  Must first be in graphics mode.