Fix mapping of intervals in Ast_mapper (ocaml#10543) (#1758)

Author: gpetiot

vendor/ocaml-4.13/ast_mapper.ml

@@ -486,7 +486,8 @@ module P = struct
     | Ppat_var s -> var ~loc ~attrs (map_loc sub s)
     | Ppat_alias (p, s) -> alias ~loc ~attrs (sub.pat sub p) (map_loc sub s)
     | Ppat_constant c -> constant ~loc ~attrs (sub.constant sub c)
-    | Ppat_interval (c1, c2) -> interval ~loc ~attrs c1 c2
+    | Ppat_interval (c1, c2) ->
+        interval ~loc ~attrs (sub.constant sub c1) (sub.constant sub c2)
     | Ppat_tuple pl -> tuple ~loc ~attrs (List.map (sub.pat sub) pl)
     | Ppat_construct (l, p) ->
         construct ~loc ~attrs (map_loc sub l)