replace usage of Py_VA_COPY with the (C99) standard va_copy
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 36f2242..c6c957b 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2683,7 +2683,7 @@
     PyObject **stack;
 
     /* Count the number of arguments */
-    Py_VA_COPY(countva, va);
+    va_copy(countva, va);
 
     n = 0;
     while (1) {