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/crossfade.c

@@ -22,7 +22,7 @@
 #include "pcm_utils.h"
 
 unsigned cross_fade_calc(float duration, float total_time,
-			 const AudioFormat * af,
+			 const struct audio_format *af,
 			 unsigned max_chunks)
 {
 	unsigned int chunks;
@@ -46,7 +46,7 @@ unsigned cross_fade_calc(float duration, float total_time,
 }
 
 void cross_fade_apply(ob_chunk * a, const ob_chunk * b,
-		      const AudioFormat * format,
+		      const struct audio_format *format,
 		      unsigned int current_chunk, unsigned int num_chunks)
 {
 	assert(current_chunk <= num_chunks);