fixup! CI: test the build and add some mingw specific tests

missing ref on the return value

Fixes python#129

Author: lazka

mingw_smoketests.py

@@ -262,7 +262,7 @@ def test_c_ext_build(self):
                                     helloworld(PyObject *self, PyObject *args)
                                     {
                                         printf("Hello World\\n");
-                                        return Py_None;
+                                        Py_RETURN_NONE;
                                     }
                                     static PyMethodDef
                                     myMethods[] = {