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/zlibmodule.c b/Modules/zlibmodule.c
index b924f84..6b818e5 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -982,7 +982,7 @@
     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*/
@@ -1013,7 +1013,7 @@
     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*/