Small correction in main.hpp so SDL2 audio class header is included w…

…hen built against SDL2. I knew I was forgetting something :)

src/main/main.hpp

@@ -3,8 +3,12 @@
 #include "globals.hpp"
 
 #ifdef COMPILE_SOUND_CODE
+#ifdef SDL2
+#include "sdl2/audio.hpp"
+#else
 #include "sdl/audio.hpp"
 #endif
+#endif
 
 namespace cannonball
 {
@@ -36,4 +40,4 @@ namespace cannonball
         STATE_GAME,
         STATE_QUIT
     };
-}
+}