added auto-quickcheck-time-limit;

--- a/src/Pure/ProofGeneral/preferences.ML	Mon Oct 01 21:19:53 2007 +0200
+++ b/src/Pure/ProofGeneral/preferences.ML	Mon Oct 01 21:19:54 2007 +0200
@@ -143,7 +143,10 @@
                 "Whether to enable debugging.",
      bool_pref Codegen.auto_quickcheck
                 "auto-quickcheck"
-                "Whether to enable quickcheck automatically."]
+                "Whether to enable quickcheck automatically.",
+     nat_pref Codegen.auto_quickcheck_time_limit
+                "auto-quickcheck-time-limit"
+                "Time limit for automatic quickcheck (in milliseconds)."]
 
 val proof_preferences =
     [bool_pref quick_and_dirty