MMDevice: we need sys->dev for WinStore

Until we can split this code out :)

modules/audio_output/mmdevice.c

@@ -74,10 +74,10 @@ static wchar_t default_device[1] = L"";
 struct aout_sys_t
 {
     aout_stream_t *stream; /**< Underlying audio output stream */
+    IMMDevice *dev; /**< Selected output device, NULL if none */
 #if !VLC_WINSTORE_APP
     audio_output_t *aout;
     IMMDeviceEnumerator *it; /**< Device enumerator, NULL when exiting */
-    IMMDevice *dev; /**< Selected output device, NULL if none */
 
     struct IMMNotificationClient device_events;
     struct IAudioSessionEvents session_events;