disabled threads -- as advertized;

--- a/src/Pure/ML-Systems/polyml-5.1.ML	Tue Nov 18 11:26:59 2008 +0100
+++ b/src/Pure/ML-Systems/polyml-5.1.ML	Tue Nov 18 13:19:13 2008 +0100
@@ -4,7 +4,7 @@
 Compatibility wrapper for Poly/ML 5.1.
 *)
 
-open Thread;
+use "ML-Systems/thread_dummy.ML";
 use "ML-Systems/polyml_common.ML";
 use "ML-Systems/polyml_old_compiler5.ML";