changes needed for adding fairness

fixed merge of internal simprocs;

Changing "lost" from a parameter of protocol definitions to a constant. Advantages: no "lost" argument everywhere; fewer Vars in subgoals; less need for specially instantiated rules Disadvantage: can no longer prove "Agent_not_see_encrypted_key", but this theorem was never used, and its original proof was also broken the introduction of the "Notes" constructor.

Fixed delIffs to deal correctly with the D-rule

Removed redundant addsimps of Un_insert_left, which is now a default simprule

Removal of monotonicity reasoning involving "lost" and the theorem Agent_not_see_encrypted_key, which (a) is never used and (b) becomes harder to prove when Notes is available.

Now uses the Notes constructor to distinguish the Client (who has chosen M) from the Spy (who may have replayed her messages)

Moved some declarations to Message from Public and Shared

Now loads theory Event, which contains common declarations

Moving common declarations and proofs from theories "Shared" and "Public" to "Event". NB the original "Event" theory was later renamed "Shared". Addition of the Notes constructor to datatype "event".