Exit correctly on write errors

This line (from a 9-year-old commit!) causes `alsa_in` to infinite-loop when a device is unplugged, writing `err = -11` to the standard output. It's possible `-11` could be special-cased if it represents a more specific kind of error, but the program should exit gracefully with an error code in this case.

alsa_in.c

@@ -439,8 +439,8 @@ again:
     if( err < 0 ) {
 	printf( "err = %d\n", err );
 	if (xrun_recovery(alsa_handle, err) < 0) {
-	    //printf("Write error: %s\n", snd_strerror(err));
-	    //exit(EXIT_FAILURE);
+	    printf("Write error: %s\n", snd_strerror(err));
+	    exit(EXIT_FAILURE);
 	}
 	goto again;
     }