Issue #1717: rename tp_compare to tp_reserved.  I'll change the
type of tp_compare in a separate commit, for ease of reversion
should things go wrong.
diff --git a/Modules/_struct.c b/Modules/_struct.c
index 25144de..94cb303 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -1853,7 +1853,7 @@
 	0,					/* tp_print */
 	0,					/* tp_getattr */
 	0,					/* tp_setattr */
-	0,					/* tp_compare */
+	0,					/* tp_reserved */
 	0,					/* tp_repr */
 	0,					/* tp_as_number */
 	0,					/* tp_as_sequence */