cmake: add python support

FindCython.cmake was taken from
https://github.com/thewtex/cython-cmake-example. The UseCython module
works, but since it is lacking an installation target setup.py will be
used instead.

cmake/FindCython.cmake

@@ -0,0 +1,44 @@
+# Find the Cython compiler.
+#
+# This code sets the following variables:
+#
+#  CYTHON_EXECUTABLE
+#
+# See also UseCython.cmake
+
+#=============================================================================
+# Copyright 2011 Kitware, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#=============================================================================
+
+# Use the Cython executable that lives next to the Python executable
+# if it is a local installation.
+find_package( PythonInterp )
+if( PYTHONINTERP_FOUND )
+  get_filename_component( _python_path ${PYTHON_EXECUTABLE} PATH )
+  find_program( CYTHON_EXECUTABLE
+    NAMES cython cython.bat cython3
+    HINTS ${_python_path}
+    )
+else()
+  find_program( CYTHON_EXECUTABLE
+    NAMES cython cython.bat cython3
+    )
+endif()
+
+
+include( FindPackageHandleStandardArgs )
+FIND_PACKAGE_HANDLE_STANDARD_ARGS( Cython REQUIRED_VARS CYTHON_EXECUTABLE )
+
+mark_as_advanced( CYTHON_EXECUTABLE )