new test for auto_cpdef with closure functions

tests/bugs.txt

@@ -19,6 +19,7 @@ for_from_pyvar_loop_T601
 decorators_T593
 temp_sideeffects_T654
 class_scope_T671
+auto_cpdef_closures
 
 # CPython regression tests that don't current work:
 pyregr.test_threadsignals

tests/run/auto_cpdef_closures.py

+# cython: auto_cpdef=True
+# mode:run
+# tag: directive,auto_cpdef,closures
+
+def closure_func(x):
+    """
+    >>> c = closure_func(2)
+    >>> c()
+    2
+    """
+    def c():
+        return x
+    return c
+
+def generator_func():
+    """
+    >>> for i in generator_func(): print(i)
+    1
+    2
+    """
+    yield 1
+    yield 2