slightly more logical bootstrap order -- also helps to sort out proof terms extension;

--- a/src/Pure/ROOT.ML	Wed Mar 24 07:50:21 2010 -0700
+++ b/src/Pure/ROOT.ML	Wed Mar 24 21:55:30 2010 +0100
@@ -92,14 +92,14 @@
 use "term_ord.ML";
 use "term_subst.ML";
 use "old_term.ML";
-use "logic.ML";
 use "General/pretty.ML";
 use "context.ML";
 use "context_position.ML";
+use "sorts.ML";
+use "type.ML";
+use "logic.ML";
 use "Syntax/lexicon.ML";
 use "Syntax/simple_syntax.ML";
-use "sorts.ML";
-use "type.ML";
 use "config.ML";