stopped nil-ing scenario vars so that (e.g.) CoP abilities still display properly at endgame

I was getting warnings for accessing nonexistent WML containers,
   every time I moused over a hex at endgame.
Used wesnoth.lock_view directly in 1.11, played nicer with already-locked views
Added a way to invoke the menu off-turn at will, and cleaned up off-turn menus a bit