Add license header

HalfedgeDS/include/CGAL/boost/graph/graph_traits_HalfedgeDS_default.h

@@ -1,3 +1,23 @@
+// Copyright (c) 20018  GeometryFactory (France).  All rights reserved.
+//
+// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation; either version 3 of the License,
+// or (at your option) any later version.
+//
+// Licensees holding a valid commercial license may use this file in
+// accordance with the commercial license agreement provided with the software.
+//
+// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
+// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+//
+// $URL$
+// $Id$
+// SPDX-License-Identifier: LGPL-3.0+
+//
+//
+// Author(s)     : Andreas Fabri
+
 #ifndef CGAL_GRAPH_TRAITS_HALFEDGEDS_DEFAULT_H
 #define CGAL_GRAPH_TRAITS_HALFEDGEDS_DEFAULT_H