Fix for #1077, add open2 to flac and vorbis, tidy ups in cdda

This description is not clear enough.

I suggest the following:

// When this hint is set, the decoder is expected to update streamer bitrate using streamer_set_bitrate call from plugin.read function

It's not the right thing to say "display in the status bar", because status bar doesn't present e.g. in android version, still the bitrate value is used by the GUI.