Don't flag the player as won on scenario maps without enemies

[mimo]

When starting the Trade Demo map, the game immediately says that we've win and ask if we want to leave. This kind of map, useful either for debug purpose or for beginners who want to learn some aspect of the game, which have "None" victory conditions should never be stopped by such test (I suppose there is a test checking if the player have some enemies left).

[elexis]

The code responsible for flagging the last remaining player as a winner is not a victory condition but the EndGameManager. Before r18342 it would flag the remaining allies as a winner, but only there was a diplomacy change or defeat after the first turn.

So if we want to disable the winning of players without enemies on some maps, these maps should specify a new boolean which if set, hides the gamesetup option 'last man standing' and disable the AlliedVictoryCheck entirely.

[Vladislav Belov]

Nobody should win if it's the endless game