Updated cv2.cpp to support Python 3 API.

Added a header with defines to enable the module to compile with either
python 2 or 3 without changes.

modules/python/src2/pycompat.hpp

@@ -0,0 +1,64 @@
+/*M///////////////////////////////////////////////////////////////////////////////////////
+//
+//  IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
+//
+//  By downloading, copying, installing or using the software you agree to this license.
+//  If you do not agree to this license, do not download, install,
+//  copy or use the software.
+//
+//
+//                           License Agreement
+//                For Open Source Computer Vision Library
+//
+// Copyright (C) 2000-2008, Intel Corporation, all rights reserved.
+// Copyright (C) 2009-2011, Willow Garage Inc., all rights reserved.
+// Third party copyrights are property of their respective owners.
+//
+// Redistribution and use in source and binary forms, with or without modification,
+// are permitted provided that the following conditions are met:
+//
+//   * Redistribution's of source code must retain the above copyright notice,
+//     this list of conditions and the following disclaimer.
+//
+//   * Redistribution's in binary form must reproduce the above copyright notice,
+//     this list of conditions and the following disclaimer in the documentation
+//     and/or other materials provided with the distribution.
+//
+//   * The name of the copyright holders may not be used to endorse or promote products
+//     derived from this software without specific prior written permission.
+//
+// This software is provided by the copyright holders and contributors "as is" and
+// any express or implied warranties, including, but not limited to, the implied
+// warranties of merchantability and fitness for a particular purpose are disclaimed.
+// In no event shall the Intel Corporation or contributors be liable for any direct,
+// indirect, incidental, special, exemplary, or consequential damages
+// (including, but not limited to, procurement of substitute goods or services;
+// loss of use, data, or profits; or business interruption) however caused
+// and on any theory of liability, whether in contract, strict liability,
+// or tort (including negligence or otherwise) arising in any way out of
+// the use of this software, even if advised of the possibility of such damage.
+//
+//M*/
+
+// Defines for Python 2/3 compatibility.
+#ifndef __PYCOMPAT_HPP__
+#define __PYCOMPAT_HPP__
+
+#if PY_MAJOR_VERSION >= 3
+// Python3 treats all ints as longs, PyInt_X functions have been removed.
+#define PyInt_Check PyLong_Check
+#define PyInt_CheckExact PyLong_CheckExact
+#define PyInt_AsLong PyLong_AsLong
+#define PyInt_AS_LONG PyLong_AS_LONG
+#define PyInt_FromLong PyLong_FromLong
+#define PyNumber_Int PyNumber_Long
+
+// Python3 strings are unicode, these defines mimic the Python2 functionality.
+#define PyString_Check PyUnicode_Check
+#define PyString_FromString PyUnicode_FromString
+#define PyString_AsString PyUnicode_AsUTF8
+#define PyString_FromStringAndSize PyUnicode_FromStringAndSize
+#define PyString_Size PyUnicode_GET_SIZE
+#endif
+
+#endif // END HEADER GUARD