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/_elementtree.c b/Modules/_elementtree.c
index 46c19eb..ac118b4 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1379,7 +1379,7 @@
     0, /* tp_print */
     0, /* tp_getattr */
     (setattrfunc)element_setattr, /* tp_setattr */
-    0, /* tp_compare */
+    0, /* tp_reserved */
     (reprfunc)element_repr, /* tp_repr */
     0, /* tp_as_number */
     &element_as_sequence, /* tp_as_sequence */
@@ -1803,7 +1803,7 @@
     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 */
@@ -2559,7 +2559,7 @@
     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 */