slightly more standard data merge: Symtax.merge (K true) avoids equality on abstract type Pretty.T and gracefully accepts overriding, Symtab.join prefers first entry as usual;
(* ID: $Id$
To update:
cp /home/lcp/isabelle/Repos/HOL/Auth/{Message.thy,Message_lemmas.ML,Event.thy,Event_lemmas.ML,Public.thy,Public_lemmas.ML,NS_Public.thy} .
*)
use_thy "NS_Public";