SF bug #1238681:  freed pointer is used in longobject.c:long_pow().

In addition, long_pow() skipped a necessary (albeit extremely unlikely
to trigger) error check when converting an int modulus to long.

Alas, I was unable to write a test case that crashed due to either
cause.

Bugfix candidate.
diff --git a/Misc/NEWS b/Misc/NEWS
index 89583e0..27d2763 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and builtins
 -----------------
 
+- SF bug #1238681:  freed pointer is used in longobject.c:long_pow().
+
 - SF bug #1229429: PyObject_CallMethod failed to decrement some
   reference counts in some error exit cases.