Add trick to get FT right for general PointRange AND for CGAL::Point_set_3

BGL/include/CGAL/boost/graph/named_params_helper.h

@@ -267,6 +267,17 @@ namespace CGAL {
       > ::type  const_type;
     };
 
+    template<typename PointRange>
+    class GetFT
+    {
+    public:
+      typedef typename Kernel_traits<
+        typename std::iterator_traits<
+          typename PointRange::iterator
+          >::value_type
+        >::Kernel::FT type;
+    };
+
     template<typename PointRange, typename NamedParameters>
     class GetQueryPointMap
     {

Point_set_3/include/CGAL/Point_set_3.h

@@ -1180,6 +1180,13 @@ Point_set_3<Point, Vector>& operator+=(Point_set_3<Point, Vector>& ps,
 /// \cond SKIP_IN_MANUAL
 namespace Point_set_processing_3
 {
+  template<typename Point, typename Vector>
+  class GetFT<CGAL::Point_set_3<Point, Vector> >
+  {
+  public:
+    typedef typename Kernel_traits<Point>::Kernel::FT type;
+  };
+  
   namespace parameters
   {
     template <typename Point, typename Vector>

Point_set_processing_3/include/CGAL/compute_average_spacing.h

@@ -241,7 +241,7 @@ compute_average_spacing(
 
 // variant with default NP
 template <typename ConcurrencyTag, typename PointRange>
-typename Kernel_traits<typename std::iterator_traits<typename PointRange::iterator>::value_type>::Kernel::FT
+typename Point_set_processing_3::GetFT<PointRange>::type
 compute_average_spacing(
   const PointRange& points,
   unsigned int k) ///< number of neighbors.

Point_set_processing_3/include/CGAL/estimate_scale.h

@@ -731,7 +731,7 @@ estimate_global_range_scale(
 /// \cond SKIP_IN_MANUAL
 // variant with default NP
 template <typename PointRange>
-typename Kernel_traits<typename std::iterator_traits<typename PointRange::iterator>::value_type>::Kernel::FT
+typename Point_set_processing_3::GetFT<PointRange>::type
 estimate_global_range_scale(const PointRange& points)
 {
   return estimate_global_range_scale

Polyhedron/demo/Polyhedron/include/Point_set_3.h

@@ -562,6 +562,13 @@ namespace CGAL
 {
 namespace Point_set_processing_3
 {
+  template<typename Kernel>
+  class GetFT<::Point_set_3<Kernel> >
+  {
+  public:
+    typedef typename Kernel::FT type;
+  };
+  
   namespace parameters
   {
     template <typename Kernel>