AirPlay progress with synchro

components/squeezelite/buffer.c

@@ -64,6 +64,11 @@ void buf_flush(struct buffer *buf) {
 	mutex_unlock(buf->mutex);
 }
 
+void _buf_flush(struct buffer *buf) {
+	buf->readp  = buf->buf;
+	buf->writep = buf->buf;
+}
+
 // adjust buffer to multiple of mod bytes so reading in multiple always wraps on frame boundary
 void buf_adjust(struct buffer *buf, size_t mod) {
 	size_t size;