remove unused SDL2/SDL.h and physfs.h from twn_util.h, explicit usage of SDL in apps, move to Scancode enum in apps

apps/lua/game.c

@@ -1,6 +1,8 @@
 #include "twn_game_api.h"
 #include "state.h"
 
+#include <SDL2/SDL.h>
+
 #include <lua.h>
 #include <lualib.h>
 #include <lauxlib.h>