Plotters: make virtual void PLOTTER::Arc() using arc angles protected.

Using arc angles to plot an arc is really error prone due to different
options between plotters, and angles defined in Kicad, using this version of
arc plotting from Kicad is no longer allowed in Kicad code.

common/plotters/SVG_plotter.cpp

@@ -469,13 +469,6 @@ void SVG_PLOTTER::Arc( const VECTOR2I& aCenter, const EDA_ANGLE& aStartAngle,
     VECTOR2D  centre_device  = userToDeviceCoordinates( aCenter );
     double  radius_device  = userToDeviceSize( aRadius );
 
-    if( !m_yaxisReversed )   // Should be never the case
-    {
-        std::swap( startAngle, endAngle );
-        startAngle = -startAngle;
-        endAngle = -endAngle;
-    }
-
     if( m_plotMirror )
     {
         if( m_mirrorIsHorizontal )