await: SYNCHRONIZED wait!

--- a/src/Pure/Concurrent/future.ML	Mon Sep 08 00:10:41 2008 +0200
+++ b/src/Pure/Concurrent/future.ML	Mon Sep 08 00:25:34 2008 +0200
@@ -190,7 +190,7 @@
 
     fun loop () =
       (case SYNCHRONIZED (fn () => ! r) of
-        NONE => (wait (); loop ())
+        NONE => (SYNCHRONIZED (fn () => wait ()); loop ())
       | SOME res => Exn.release res);
   in loop () end;