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/platformer/scenes/ingame.c

@@ -4,6 +4,8 @@
 
 #include "twn_game_api.h"
 
+#include <SDL2/SDL.h>
+
 
 static void ingame_tick(State *state) {
     SceneIngame *scn = (SceneIngame *)state->scene;

apps/platformer/scenes/title.c

@@ -5,6 +5,8 @@
 
 #include "twn_game_api.h"
 
+#include <SDL2/SDL.h>
+
 #include <stdio.h>