Use a typedef for the sound instance handle

apps/openmw/mwsound/sound.hpp

@@ -1,7 +1,7 @@
 #ifndef GAME_SOUND_SOUND_H
 #define GAME_SOUND_SOUND_H
 
-#include "soundmanagerimp.hpp"
+#include "sound_output.hpp"
 
 namespace MWSound
 {
@@ -20,7 +20,7 @@ namespace MWSound
         float mFadeOutTime;
 
     protected:
-        void *mHandle;
+        Sound_Instance mHandle;
 
         friend class Sound_Output;
         friend class OpenAL_Output;

apps/openmw/mwsound/sound_output.hpp

@@ -3,11 +3,10 @@
 
 #include <string>
 #include <memory>
+#include <vector>
 
 #include "soundmanagerimp.hpp"
 
-#include "../mwworld/ptr.hpp"
-
 namespace MWSound
 {
     class SoundManager;
@@ -17,6 +16,8 @@ namespace MWSound
 
     // An opaque handle for the implementation's sound buffers.
     typedef void *Sound_Handle;
+    // An opaque handle for the implementation's sound instances.
+    typedef void *Sound_Instance;
 
     class Sound_Output
     {