Use a separate thread in test_codec, with the same (IRAM) stack as the main codec thread. Add a function to the plugin API to steal the codec thread, which test_codec copies and then restores. Now libmad can be benchmarked.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@13347 a1c6a512-1295-4272-9138-f99709370657

apps/plugin.h

@@ -611,6 +611,7 @@ struct plugin_api {
     bool (*get_metadata)(struct track_info* track, int fd, const char* trackname,
                          bool v1first);
     const char *(*get_codec_filename)(int cod_spec);
+    void (*steal_codec_stack)(unsigned char** stack, size_t* size);
 #endif
 };