macosx: fixed volume normalizer prefs and crash when saving the Growl option in combination with some config sets

It is a preliminary work.

It is looking more natural.

It allows to use hw decoding (whereas it was always disabled).
It workaround a bug in ffmpeg/libav.

It avoid tearing depending on the default settings.

 * Add a dispatcher method for tracklist properties
 * Implement Tracks and CanEditTracks

restricted to the audio and video filters.

This happen when p_vids->p_bih->biSize - sizeof( BITMAPINFOHEADER ) = 0
and the data is in p_vids->i_chunk_size, because then p_extra == NULL.

This solves the fruity sample crash but doesn't fix the palette

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

It allows to give them a category (vout display).