builtin_complex(): Nailed memory leak. This one's in the instance

test for classes with a __complex__() method.  The attribute is pulled
out of the instance with PyObject_GetAttr() but this transfers
ownership and the function object was never DECREF'd.

Python/bltinmodule.c

@@ -409,6 +409,7 @@ builtin_complex(self, args)
 				return NULL;
 			r = PyEval_CallObject(f, args);
 			Py_DECREF(args);
+			Py_DECREF(f);
 			if (r == NULL)
 				return NULL;
 			own_r = 1;