fix build with sdl2-ttf 2.24.0

Index: src/engine/video/text.h
--- src/engine/video/text.h.orig
+++ src/engine/video/text.h
@@ -28,7 +28,7 @@
 
 #include <map>
 
-typedef struct _TTF_Font TTF_Font;
+#include <SDL_ttf.h>
 
 namespace vt_video
 {
