use_thy: removed obsolete ML_Context.save;

--- a/src/Pure/Isar/isar_syn.ML	Wed Mar 26 20:14:36 2008 +0100
+++ b/src/Pure/Isar/isar_syn.ML	Wed Mar 26 20:14:37 2008 +0100
@@ -947,7 +947,8 @@
 
 val _ =
   OuterSyntax.improper_command "use_thy" "use theory file" K.diag
-    (P.name >> (Toplevel.no_timing oo IsarCmd.use_thy));
+    (P.name >> (fn name =>
+      Toplevel.no_timing o Toplevel.imperative (fn () => ThyInfo.use_thy name)));
 
 val _ =
   OuterSyntax.improper_command "touch_thy" "outdate theory, including descendants" K.diag