HUDMessage: use plain black for backgrounds.
NGCFlag: don't run answered_no if answered_yes has run; require existence of title message.
NGCGame: send StartWar and FinishWar messages to pieces instead of modifying them here; stop the clocks on engine and script errors and when declaring war.
NGCPiece: respond to StartWar and FinishWar messages with appropriate changes.
Use sto* and to_string methods.
Update for historic ThiefLib changes.