add close function wrapper

src/beep.c

@@ -152,6 +152,12 @@ int beep_init()
 	return 0;
 }
 
+int beep_close()
+{
+	buzzer_stop();
+	return 0;
+}
+
 
 int beep_test(void)
 {

src/beep.h

@@ -36,3 +36,4 @@ int beep_test(void);
 // compatibility to old interface
 int beep(double freq_hz, double duration_sec);
 int beep_init();
+int beep_close();