fix alsa errors being duplicated to stderr

stepmania/src/arch/Sound/ALSA9Helpers.cpp

@@ -68,7 +68,6 @@ void Alsa9Buf::GetSoundCardDebugInfo()
 		return;
 	done = true;
 
-
 	int card = -1;
 	while( snd_card_next( &card ) >= 0 && card >= 0 )
 	{
@@ -123,10 +122,17 @@ void Alsa9Buf::GetSoundCardDebugInfo()
 		LOG->Info( "No ALSA sound cards were found.");
 }
 
+void Alsa9Buf::ErrorHandler(const char *file, int line, const char *function, int err, const char *fmt, ...)
+{
+/* NOP */
+}
+
 Alsa9Buf::Alsa9Buf( hw hardware, int channels_, int samplerate_ )
 {
 	GetSoundCardDebugInfo();
 		
+	snd_lib_error_set_handler( ErrorHandler );
+	
 	channels = channels_;
 	samplerate = samplerate_;
 	samplebits = 16;

stepmania/src/arch/Sound/ALSA9Helpers.h

@@ -20,6 +20,8 @@ private:
 	bool Recover( int r );
 	bool SetHWParams();
 
+	static void ErrorHandler(const char *file, int line, const char *function, int err, const char *fmt, ...);
+		
 public:
 	static void GetSoundCardDebugInfo();