Add determinant(Vector_2, Vector_2)

Add determinant(Vector_3, Vector_3, Vector_3)
And corresponding functor.

Cartesian_kernel/include/CGAL/Cartesian/function_objects.h

@@ -804,6 +804,40 @@ namespace CartesianKernelFunctors {
     { return t.area(); }
   };
 
+  template <typename K>
+  class Compute_determinant_2
+  {
+    typedef typename K::FT                FT;
+    typedef typename K::Vector_2          Vector_2;
+  public:
+    typedef FT               result_type;
+    typedef Arity_tag< 2 >   Arity;
+
+    result_type
+    operator()(const Vector_2& v, const Vector_2& w) const
+    {
+	return det2x2_by_formula(v.x(), v.y(), w.x(), w.y());
+    }
+  };
+
+  template <typename K>
+  class Compute_determinant_3
+  {
+    typedef typename K::FT                FT;
+    typedef typename K::Vector_3          Vector_3;
+  public:
+    typedef FT               result_type;
+    typedef Arity_tag< 3 >   Arity;
+
+    result_type
+    operator()(const Vector_3& v, const Vector_3& w, const Vector_3& t) const
+    {
+	return det3x3_by_formula(v.x(), v.y(), v.z(),
+                                 w.x(), w.y(), w.z(),
+                                 t.x(), t.y(), t.z());
+    }
+  };
+
   template <typename K>
   class Compute_scalar_product_2
   {