add .py test for 'binding' effect

--HG--
rename : tests/run/function_as_method_T494.pyx => tests/run/function_as_method_py_T494.py

tests/run/function_as_method_py_T494.py

+# ticket: 494
+
+__doc__ = """
+    >>> A.foo = foo
+    >>> print A().foo()
+    True
+"""
+
+class A:
+    pass
+
+def foo(self):
+    return self is not None