starting SDL port, refactoring

platform/common/mp3_dummy.c

@@ -0,0 +1,23 @@
+/*
+ * dummy/none mp3 code
+ * (C) notaz, 2013
+ *
+ * This work is licensed under the terms of MAME license.
+ * See COPYING file in the top-level directory.
+ */
+
+#include "mp3.h"
+#include <pico/pico.h>
+
+int mp3_get_bitrate(void *f_, int len)
+{
+	return -1;
+}
+
+void mp3_start_play(void *f_, int pos)
+{
+}
+
+void mp3_update(int *buffer, int length, int stereo)
+{
+}