Use Py_intptr_t to store the difference between two pointers, instead of int

Fix a compiler warning on Windows 64-bit
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index 3cf00d5..d4f8048 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -1009,7 +1009,7 @@
 static PyObject *
 wrapper_richcompare(PyObject *a, PyObject *b, int op)
 {
-    int result;
+    Py_intptr_t result;
     PyObject *v;
     PyWrapperDescrObject *a_descr, *b_descr;