Issue python#128: Fix pickling of the module 'stackless'.

Correct the name of the function __reduce_ex__(). And add a test case.

https://bitbucket.org/stackless-dev/stackless/issues/128
(grafted from 7db74e8ee4e77ad617dc5467da0efd3f3b7cf925)

Lib/stackless.py

@@ -18,7 +18,7 @@
 
 def __reduce__():
     return "stackless"
-def __reduce_ex_(*args):
+def __reduce_ex__(*args):
     return "stackless"
 
 # Backwards support for unpickling older pickles, even from 2.7

Stackless/changelog.txt

@@ -9,6 +9,9 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://bitbucket.org/stackless-dev/stackless/issues/128
+  Fix pickling of the module 'stackless'.
+
 - https://bitbucket.org/stackless-dev/stackless/issues/127
   Disable the Stackless specific code for pickling 'iterator' and
   'callable_iterator' objects. C-Python 3.3 already pickles them.

Stackless/unittests/test_pickle.py

@@ -645,6 +645,10 @@ def _test(self, obj, *attributes, **kw):
             # refer to the same objects
             self.assertIs(value_c, value_obj)
 
+    def test_module_stackless(self):
+        # test for issue 128
+        self.assertIs(stackless, copy.copy(stackless))
+
     def test_code(self):
         def f():
             pass