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/sha512module.c b/Modules/sha512module.c
index 472b158..7d67a23 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -611,7 +611,7 @@
     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*/
@@ -645,7 +645,7 @@
     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*/