add header

--- a/src/HOLCF/Discrete.thy	Fri Mar 04 23:23:47 2005 +0100
+++ b/src/HOLCF/Discrete.thy	Fri Mar 04 23:25:06 2005 +0100
@@ -6,6 +6,8 @@
 Discrete CPOs.
 *)
 
+header {* Discrete cpo types *}
+
 theory Discrete
 imports Cont Datatype
 begin