updated docs

--- a/src/Doc/Datatypes/Datatypes.thy	Fri Oct 18 14:58:02 2013 +0200
+++ b/src/Doc/Datatypes/Datatypes.thy	Fri Oct 18 15:00:40 2013 +0200
@@ -786,6 +786,10 @@
 
 \end{description}
 \end{indentblock}
+
+\noindent
+In addition, equational versions of @{text t.disc} are registered with the @{text "[code]"}
+attribute.
 *}