Add ARRAY_SIZE macro, and use it where possible.
diff --git a/py/compile.c b/py/compile.c
index ee735a8..532e29a 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -86,8 +86,8 @@
 STATIC const mp_map_t mp_constants_map = {
     .all_keys_are_qstrs = 1,
     .table_is_fixed_array = 1,
-    .used = sizeof(mp_constants_table) / sizeof(mp_map_elem_t),
-    .alloc = sizeof(mp_constants_table) / sizeof(mp_map_elem_t),
+    .used = ARRAY_SIZE(mp_constants_table),
+    .alloc = ARRAY_SIZE(mp_constants_table),
     .table = (mp_map_elem_t*)mp_constants_table,
 };