Add a public typedef FaceGraph to Scene_surface_mesh_item and Scene_polyhedron_item.

Polyhedron/demo/Polyhedron/Scene_polyhedron_item.h

@@ -28,6 +28,7 @@ class SCENE_POLYHEDRON_ITEM_EXPORT Scene_polyhedron_item
     Q_INTERFACES(CGAL::Three::Scene_zoomable_item_interface)
     Q_PLUGIN_METADATA(IID "com.geometryfactory.PolyhedronDemo.ZoomInterface/1.0")
 public:
+  typedef Polyhedron FaceGraph;
     enum STATS {
       NB_VERTICES = 0,
       NB_CONNECTED_COMPOS,

Polyhedron/demo/Polyhedron/Scene_surface_mesh_item.h

@@ -29,6 +29,7 @@ public:
   typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
   typedef Kernel::Point_3 Point;
   typedef CGAL::Surface_mesh<Point> SMesh;
+  typedef SMesh FaceGraph;
   typedef boost::graph_traits<SMesh>::face_descriptor face_descriptor;
 
   Scene_surface_mesh_item();