doxygen: manually move SDL_CloseAudioDevice docs from wiki.

Apparently we don't fill these in from the wiki if the function doesn't
have _any_ documentation already. That's a bug, I think.

include/SDL_audio.h

@@ -1151,6 +1151,27 @@ extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
  * \sa SDL_OpenAudio
  */
 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
+
+/**
+ * Use this function to shut down audio processing and close the audio device.
+ *
+ * The application should close open audio devices once they are no longer
+ * needed. Calling this function will wait until the device's audio callback
+ * is not running, release the audio hardware and then clean up internal
+ * state. No further audio will play from this device once this function
+ * returns.
+ *
+ * This function may block briefly while pending audio data is played by the
+ * hardware, so that applications don't drop the last buffer of data they
+ * supplied.
+ *
+ * The device ID is invalid as soon as the device is closed, and is eligible
+ * for reuse in a new SDL_OpenAudioDevice() call immediately.
+ *
+ * \param dev an audio device previously opened with SDL_OpenAudioDevice()
+ *
+ * \sa SDL_OpenAudioDevice
+ */
 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
 
 /* Ends C function definitions when using C++ */