add header

--- a/src/HOL/Real/Float.thy	Tue Sep 26 17:33:04 2006 +0200
+++ b/src/HOL/Real/Float.thy	Tue Sep 26 22:37:51 2006 +0200
@@ -3,6 +3,8 @@
     Author: Steven Obua
 *)
 
+header {* Floating Point Representation of the Reals *}
+
 theory Float
 imports Real
 begin