tuned whitespace

--- a/src/HOL/Library/Dlist.thy	Tue Jul 17 23:07:51 2012 +0200
+++ b/src/HOL/Library/Dlist.thy	Tue Jul 17 23:11:24 2012 +0200
@@ -180,10 +180,12 @@
 enriched_type map: map
   by (simp_all add: List.map.id remdups_map_remdups fun_eq_iff dlist_eq_iff)
 
+
 subsection {* Quickcheck generators *}
 
 quickcheck_generator dlist predicate: distinct constructors: empty, insert
 
+
 hide_const (open) member fold foldr empty insert remove map filter null member length fold
 
 end