Christian Sternagel [Wed, 29 Aug 2012 16:25:35 +0900] rev 49085
introduced "sub" as abbreviation for "emb (op =)";
Sublist_Order is now based on Sublist.sub;
simplified and moved most lemmas on sub from Sublist_Order to Sublist;
Sublist_Order merely contains ord and order instances for sub plus some lemmas on the strict part of the order