Stop the "ao", "pulse" and "sndio" backends from complaining about the new output rate and format information.

audio_ao.c

@@ -170,10 +170,6 @@ static void deinit(void) {
 }
 
 static void start(int sample_rate, int sample_format) {
-  if (sample_rate != 0)
-    die("unexpected sample rate!");
-  if (sample_format != 0)
-    die("unexpected sample format!");
 }
 
 static void play(short buf[], int samples) { ao_play(dev, (char *)buf, samples * 4); }

audio_pulse.c

@@ -111,10 +111,6 @@ static void deinit(void) {
 }
 
 static void start(int sample_rate, int sample_format) {
-  if (sample_rate != 0)
-    die("unexpected sample rate!");
-  if (sample_format != 0)
-    die("unexpected sample format!");
 }
 
 static void play(short buf[], int samples) {

audio_sndio.c

@@ -54,10 +54,6 @@ static int init(int argc, char **argv) {
 static void deinit(void) { sio_close(sio); }
 
 static void start(int sample_rate) {
-  if (sample_rate != par.rate)
-    die("unexpected sample rate!");
-  if (sample_format != 0)
-    die("unexpected sample format!");
   sio_start(sio);
 }