moved markup.ML before position.ML;

--- a/src/Pure/General/ROOT.ML	Sat Jul 07 11:09:40 2007 +0200
+++ b/src/Pure/General/ROOT.ML	Sat Jul 07 12:16:13 2007 +0200
@@ -19,10 +19,10 @@
 use "name_space.ML";
 use "seq.ML";
 use "susp.ML";
+use "markup.ML";
 use "position.ML";
 use "path.ML";
 use "url.ML";
 use "file.ML";
 use "buffer.ML";
 use "history.ML";
-use "markup.ML";