Use OCCT Handle macro for Handle_ classes

This is the result of running OCCT's upgrade script provided
with OCCT 7.0. See
https://www.opencascade.com/content/freecad-occt710-and-windows-rtti-data-missing#comment-form
and
https://www.forum.freecadweb.org/viewtopic.php?f=4&t=21405&start=120#p169019
for why this is necessary for OCCT >= 7.1

src/Mod/Raytracing/App/PovTools.cpp

@@ -463,7 +463,7 @@ void PovTools::transferToArray(const TopoDS_Face& aFace,gp_Vec** vertices,gp_Vec
         gp_Dir clNormal;
 
         try {
-            Handle_Geom_Surface Surface = BRep_Tool::Surface(aFace);
+            Handle(Geom_Surface) Surface = BRep_Tool::Surface(aFace);
 
             gp_Pnt vertex((*vertices)[i].XYZ());
 //     gp_Pnt vertex((*vertices)[i][0], (*vertices)[i][1], (*vertices)[i][2]);