Use `memoize` instead of `tabulate` in `delta`.

demos/brz/Brzozowski.ml

@@ -301,11 +301,10 @@ let nullable : regexp -> bool =
    star.) More precisely, for every character [a], [delta a] is a function of
    type [regexp -> regexp]: we memoize every function [delta a] separately. *)
 
-
 let delta : Char.t -> regexp -> regexp =
-  let module T = Tabulate.ForHashedType(Char)(Char) in
+  let module C = Memoize.ForHashedType(Char) in
   let module M = Memoize.ForHashedType(R) in
-  T.tabulate (fun a ->
+  C.memoize (fun a ->
     M.fix (fun delta e ->
       match skeleton e with
       | EEpsilon ->