made SML/97 happy;

--- a/src/Pure/pure_thy.ML	Mon Nov 03 09:58:06 1997 +0100
+++ b/src/Pure/pure_thy.ML	Mon Nov 03 11:46:25 1997 +0100
@@ -69,7 +69,9 @@
 
 in
 
-val theorems_data = (theoremsK, (mk_empty (), mk_empty, mk_empty, print));
+val theorems_data:
+  string * (exn * (exn -> exn) * (exn * exn -> exn) * (exn -> unit)) =
+    (theoremsK, (mk_empty (), mk_empty, mk_empty, print));
 
 end;