renamed body_context_node to presentation_context;

--- a/src/Pure/Isar/isar_output.ML	Wed Oct 11 00:31:38 2006 +0200
+++ b/src/Pure/Isar/isar_output.ML	Wed Oct 11 00:32:02 2006 +0200
@@ -115,7 +115,7 @@
 fun args scan f src node : string =
   let
     val loc = if ! locale = "" then NONE else SOME (! locale);
-    val (ctxt, x) = syntax scan src (Toplevel.body_context_node node loc);
+    val (ctxt, x) = syntax scan src (Toplevel.presentation_context node loc);
   in f src ctxt x end;