enat is a complete_linorder instance

--- a/src/HOL/Library/Extended_Nat.thy	Tue Jul 26 12:44:36 2011 +0200
+++ b/src/HOL/Library/Extended_Nat.thy	Tue Jul 26 13:50:03 2011 +0200
@@ -564,6 +564,7 @@
 qed (simp_all add: inf_enat_def sup_enat_def)
 end
 
+instance enat :: complete_linorder ..
 
 subsection {* Traditional theorem names *}