Add support for custom pad shape. Full support in DRC and PnS.

add option to use shape or convex hull as clearance area in zones.
simplify code to handle clearance area

pcbnew/plot_brditems_plotter.cpp

@@ -182,6 +182,19 @@ void BRDITEMS_PLOTTER::PlotPad( D_PAD* aPad, COLOR4D aColor, EDA_DRAW_MODE_T aPl
                                       aPad->GetOrientation(), aPlotMode, &gbr_metadata );
         break;
 
+    case PAD_SHAPE_CUSTOM:
+        {
+        SHAPE_POLY_SET polygons;
+        aPad->MergeBasicShapesAsPolygon(&polygons, 64 );
+
+        if( polygons.OutlineCount() == 0 )
+            break;
+
+        aPad->BasicShapesAsPolygonToBoardPosition( &polygons, shape_pos, aPad->GetOrientation() );
+        m_plotter->FlashPadCustom( shape_pos, aPad->GetSize(), &polygons, aPlotMode, &gbr_metadata );
+        }
+        break;
+
     case PAD_SHAPE_RECT:
     default:
         m_plotter->FlashPadRect( shape_pos, aPad->GetSize(),