audio_format: converted typedef AudioFormat to struct audio_format

Get rid of CamelCase, and don't use a typedef, so we can
forward-declare it, and unclutter the include dependencies.

src/audioOutputs/audioOutput_alsa.c

@@ -123,7 +123,7 @@ static int alsa_testDefault(void)
 static int alsa_openDevice(AudioOutput * audioOutput)
 {
 	AlsaData *ad = audioOutput->data;
-	AudioFormat *audioFormat = &audioOutput->outAudioFormat;
+	struct audio_format *audioFormat = &audioOutput->outAudioFormat;
 	snd_pcm_format_t bitformat;
 	snd_pcm_hw_params_t *hwparams;
 	snd_pcm_sw_params_t *swparams;

src/audioOutputs/audioOutput_jack.c

@@ -118,7 +118,7 @@ static void jack_finishDriver(AudioOutput *audioOutput)
 static int srate(mpd_unused jack_nframes_t rate, void *data)
 {
 	JackData *jd = (JackData *) ((AudioOutput*) data)->data;
- 	AudioFormat *audioFormat = &(((AudioOutput*) data)->outAudioFormat);
+ 	struct audio_format *audioFormat = &(((AudioOutput*) data)->outAudioFormat);
 
  	audioFormat->sampleRate = (int)jack_get_sample_rate(jd->client);
 
@@ -183,7 +183,7 @@ static void shutdown_callback(void *arg)
 static void set_audioformat(AudioOutput *audioOutput)
 {
 	JackData *jd = audioOutput->data;
-	AudioFormat *audioFormat = &audioOutput->outAudioFormat;
+	struct audio_format *audioFormat = &audioOutput->outAudioFormat;
 
 	audioFormat->sampleRate = (int) jack_get_sample_rate(jd->client);
 	DEBUG("samplerate = %d\n", audioFormat->sampleRate);

src/audioOutputs/audioOutput_oss.c

@@ -484,7 +484,7 @@ static int oss_openDevice(AudioOutput * audioOutput)
 {
 	int ret;
 	OssData *od = audioOutput->data;
-	AudioFormat *audioFormat = &audioOutput->outAudioFormat;
+	struct audio_format *audioFormat = &audioOutput->outAudioFormat;
 
 	od->channels = (mpd_sint8)audioFormat->channels;
 	od->sampleRate = audioFormat->sampleRate;

src/audioOutputs/audioOutput_pulse.c

@@ -112,7 +112,7 @@ static int pulse_testDefault(void)
 static int pulse_openDevice(AudioOutput * audioOutput)
 {
 	PulseData *pd;
-	AudioFormat *audioFormat;
+	struct audio_format *audioFormat;
 	pa_sample_spec ss;
 	time_t t;
 	int error;

src/audioOutputs/audioOutput_shout.c

@@ -66,7 +66,7 @@ typedef struct _ShoutData {
 	Timer *timer;
 
 	/* just a pointer to audioOutput->outAudioFormat */
-	AudioFormat *audioFormat;
+	struct audio_format *audioFormat;
 } ShoutData;
 
 static ShoutData *newShoutData(void)