work around type redefinition errors in SDL_immdevice.h

src/core/windows/SDL_immdevice.h

@@ -26,20 +26,20 @@
 #include <mmdeviceapi.h>
 #include <mmreg.h>
 
-typedef struct SDL_AudioDevice SDL_AudioDevice; // this is defined in src/audio/SDL_sysaudio.h
+struct SDL_AudioDevice; // defined in src/audio/SDL_sysaudio.h
 
 typedef struct SDL_IMMDevice_callbacks
 {
-    void (*audio_device_disconnected)(SDL_AudioDevice *device);
-    void (*default_audio_device_changed)(SDL_AudioDevice *new_default_device);
+    void (*audio_device_disconnected)(struct SDL_AudioDevice *device);
+    void (*default_audio_device_changed)(struct SDL_AudioDevice *new_default_device);
 } SDL_IMMDevice_callbacks;
 
 bool SDL_IMMDevice_Init(const SDL_IMMDevice_callbacks *callbacks);
 void SDL_IMMDevice_Quit(void);
-bool SDL_IMMDevice_Get(SDL_AudioDevice *device, IMMDevice **immdevice, bool recording);
-void SDL_IMMDevice_EnumerateEndpoints(SDL_AudioDevice **default_playback, SDL_AudioDevice **default_recording);
-LPGUID SDL_IMMDevice_GetDirectSoundGUID(SDL_AudioDevice *device);
-LPCWSTR SDL_IMMDevice_GetDevID(SDL_AudioDevice *device);
-void SDL_IMMDevice_FreeDeviceHandle(SDL_AudioDevice *device);
+bool SDL_IMMDevice_Get(struct SDL_AudioDevice *device, IMMDevice **immdevice, bool recording);
+void SDL_IMMDevice_EnumerateEndpoints(struct SDL_AudioDevice **default_playback, struct SDL_AudioDevice **default_recording);
+LPGUID SDL_IMMDevice_GetDirectSoundGUID(struct SDL_AudioDevice *device);
+LPCWSTR SDL_IMMDevice_GetDevID(struct SDL_AudioDevice *device);
+void SDL_IMMDevice_FreeDeviceHandle(struct SDL_AudioDevice *device);
 
 #endif // SDL_IMMDEVICE_H