made SML/NJ happy

--- a/src/HOL/Tools/ATP/atp_translate.ML	Thu Sep 08 12:23:11 2011 +0200
+++ b/src/HOL/Tools/ATP/atp_translate.ML	Fri Sep 09 14:30:57 2011 +0200
@@ -1899,7 +1899,8 @@
            let
              val (pred_sym, in_conj) =
                case Symtab.lookup sym_tab s of
-                 SOME {pred_sym, in_conj, ...} => (pred_sym, in_conj)
+                 SOME ({pred_sym, in_conj, ...} : sym_info) =>
+                 (pred_sym, in_conj)
                | NONE => (false, false)
              val decl_sym =
                (case type_enc of