for compatibility, generate recursor arguments in the same order as old package

--- a/src/HOL/BNF/Tools/bnf_fp_def_sugar.ML	Fri Apr 26 14:14:54 2013 +0200
+++ b/src/HOL/BNF/Tools/bnf_fp_def_sugar.ML	Fri Apr 26 14:14:55 2013 +0200
@@ -80,10 +80,10 @@
   let val ps = map unzipf xs in
     (* The first line below gives the preferred order. The second line is for compatibility with the
        old datatype package: *)
+(*
     maps (op @) ps
-(*
+*)
     maps fst ps @ maps snd ps
-*)
   end;
 
 fun mk_flip (x, Type (_, [T1, Type (_, [T2, T3])])) =