Make all conversions between Point and Weighted_point explicit

Also doc changes

Cartesian_kernel/include/CGAL/Cartesian/Weighted_point_2.h

@@ -53,6 +53,7 @@ public:
   Weighted_pointC2(const Origin &o)
     : base(o, 0) {}
 
+  explicit
   Weighted_pointC2 (const Point_2 &p)
     : base(p,0)
   {}

Homogeneous_kernel/include/CGAL/Homogeneous/Weighted_point_2.h

@@ -53,6 +53,7 @@ public:
   Weighted_pointH2(const Origin &o)
     : base(o, 0) {}
 
+  explicit
   Weighted_pointH2 (const Point_2 &p)
     : base(p,0)
   {}

Kernel_23/doc/Kernel_23/CGAL/Point_2.h

@@ -85,8 +85,11 @@ Point_2(const Kernel::FT &x, const Kernel::FT &y);
 
 /*!
 introduces a point from a weighted point.
+
+\warning The `explicit` keyword is used to not have accidental implicit conversions
+         between Point_2 and Weighted_point_2.
 */
-Point_2(const Kernel::Weighted_point_2 &wp);
+explicit Point_2(const Kernel::Weighted_point_2 &wp);
 
 /// @}
 

Kernel_23/doc/Kernel_23/CGAL/Point_3.h

@@ -66,8 +66,11 @@ Point_3(const Kernel::FT &x, const Kernel::FT &y, const Kernel::FT &z);
 
 /*!
 introduces a point from a weighted point.
+
+\warning The `explicit` keyword is used to not have accidental implicit conversions
+         between Point_3 and Weighted_point_3.
 */
-Point_3(const Kernel::Weighted_point_3 &wp);
+explicit Point_3(const Kernel::Weighted_point_3 &wp);
 
 /// @}
 

Kernel_23/doc/Kernel_23/CGAL/Weighted_point_2.h

@@ -47,6 +47,9 @@ public:
 
   /*!
   introduces a weighted point from point `p` and weight `0`.
+
+  \warning The `explicit` keyword is used to not have accidental implicit conversions
+           between Point_2 and Weighted_point_2.
   */
   Weighted_point_2(const Point_2<Kernel>& p);
 

Kernel_23/include/CGAL/Point_2.h

@@ -78,11 +78,10 @@ public:
     : RPoint_2(p)
   {}
 
-#if 0
+  explicit
   Point_2(const Weighted_point_2& wp)
     : Rep(wp.point())
   {}
-#endif
 
   template < typename T1, typename T2 >
   Point_2(const T1 &x, const T2 &y)

Kernel_23/include/CGAL/Point_3.h

@@ -74,11 +74,12 @@ public:
 
   Point_3(const Rep& p)
       : Rep(p) {}
-#if 0
+
+  explicit
   Point_3(const Weighted_point_3& wp)
     : Rep(wp.point())
   {}
-#endif
+
   template < typename T1, typename T2, typename T3 >
   Point_3(const T1& x, const T2& y, const T3& z)
     : Rep(typename R::Construct_point_3()(Return_base_tag(), x, y, z))

Kernel_23/include/CGAL/Weighted_point_2.h

@@ -76,7 +76,8 @@ public:
   Weighted_point_2(const Rep& p)
       : Rep(p) {}
 
-  explicit Weighted_point_2(const Point_2& p)
+  explicit
+  Weighted_point_2(const Point_2& p)
     : Rep(typename R::Construct_weighted_point_2()(Return_base_tag(), p, 0))
   {}
 

Kernel_23/include/CGAL/Weighted_point_3.h

@@ -78,7 +78,8 @@ public:
   Weighted_point_3(const Rep& p)
       : Rep(p) {}
 
-  explicit Weighted_point_3(const Point_3& p)
+  explicit
+  Weighted_point_3(const Point_3& p)
     : Rep(typename R::Construct_weighted_point_3()(Return_base_tag(), p, 0))
   {}