Split sound_openal_internal into serval files

src/client/sound/sound_openal.cpp

@@ -22,7 +22,9 @@ with this program; ifnot, write to the Free Software Foundation, Inc.,
 */
 
 #include "sound_openal.h"
-#include "sound_openal_internal.h"
+
+#include "sound_singleton.h"
+#include "proxy_sound_manager.h"
 
 std::shared_ptr<SoundManagerSingleton> g_sound_manager_singleton;