Move roomchangedir off of Game

This is a temporary variable that doesn't need to be on Game. It is
guaranteed to be initialized every time mapclass::gotoroom() gets
called, so it's safe to move it off.

desktop_version/src/Game.h

@@ -215,7 +215,7 @@ public:
     int door_right;
     int door_up;
     int door_down;
-    int roomx, roomy, roomchangedir;
+    int roomx, roomy;
     int prevroomx, prevroomy;
 
     int savex, savey, saverx, savery;