Revert "Fix build with 4.05"

In order to reduce the difference between the 4.1 maintenance branch and
master, revert the old 4.05 fixes and apply the one's from the 4.1
branch instead

This reverts commit b6b02c2.

src/ppx_deriving.cppo.ml

@@ -12,21 +12,6 @@ open Parsetree
 open Ast_helper
 open Ast_convenience
 
-#if OCAML_VERSION >= (4, 05, 0)
-module Typ = struct
-  include Typ
-
-  let poly ?(loc= !Ast_helper.default_loc) ?attrs vars ty =
-    let vars = List.map (fun txt -> { Asttypes.loc; txt }) vars in
-    Typ.poly ~loc ?attrs vars ty
-end
-
-let rm_poly_locs =
-  List.map (fun x -> x.Asttypes.txt)
-#else
-let rm_poly_locs x = x
-#endif
-
 type deriver = {
   name : string ;
   core_type : (core_type -> expression) option;
@@ -340,7 +325,6 @@ let free_vars_in_core_type typ =
       List.map free_in xs |> List.concat
     | { ptyp_desc = Ptyp_alias (x, name) } -> [name] @ free_in x
     | { ptyp_desc = Ptyp_poly (bound, x) } ->
-      let bound = rm_poly_locs bound in
       List.filter (fun y -> not (List.mem y bound)) (free_in x)
     | { ptyp_desc = Ptyp_variant (rows, _, _) } ->
       List.map (