Regroup OpenInventor I/O headers

Stream_support/include/CGAL/IO/OI.h

@@ -0,0 +1,21 @@
+// Copyright (c) 2018  GeometryFactory Sarl (France).
+// All rights reserved.
+//
+// Licensees holding a valid commercial license may use this file in
+// accordance with the commercial license agreement provided with the software.
+//
+// This file is part of CGAL (www.cgal.org)
+//
+// $URL$
+// $Id$
+// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
+//
+// Author(s)     : Lutz Kettner
+
+#ifndef CGAL_IO_OI_H
+#define CGAL_IO_OI_H
+
+#include <CGAL/IO/OI/File_writer_inventor.h>
+#include <CGAL/IO/OI/Inventor_ostream.h>
+
+#endif // CGAL_IO_OI_H