timer: constant pointers

The audio_format argument to timer_new() should be constant, because
it is not modified.  The same is true for ShoutData.audioFormat.

src/audioOutputs/audioOutput_shout.c

@@ -65,7 +65,7 @@ typedef struct _ShoutData {
 	Timer *timer;
 
 	/* just a pointer to audioOutput->outAudioFormat */
-	struct audio_format *audioFormat;
+	const struct audio_format *audioFormat;
 } ShoutData;
 
 static ShoutData *newShoutData(void)

src/timer.c

@@ -30,7 +30,7 @@ static uint64_t now(void)
 	return ((uint64_t)tv.tv_sec * 1000000) + tv.tv_usec;
 }
 
-Timer *timer_new(struct audio_format *af)
+Timer *timer_new(const struct audio_format *af)
 {
 	Timer *timer;
 

src/timer.h

@@ -29,7 +29,7 @@ typedef struct _Timer {
 	int rate;
 } Timer;
 
-Timer *timer_new(struct audio_format *af);
+Timer *timer_new(const struct audio_format *af);
 
 void timer_free(Timer *timer);