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/Python/Python-ast.c b/Python/Python-ast.c
index cf79b37..1e85b2f 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -479,7 +479,7 @@
     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 */