Add function Game::anything_unlocked()

This will be a useful shorthand to ask "do we have the Secret Lab, or
any Time Trial, or Intermission replays, or No Death Mode, or Flip Mode
unlocked?"

desktop_version/src/Game.h

@@ -286,6 +286,7 @@ public:
 
     std::vector<int> unlock;
     std::vector<int> unlocknotify;
+    bool anything_unlocked();
     int stat_trinkets;
     bool fullscreen;
     int bestgamedeaths;