+ added --meta-title/author/artist/genre/copyright/description/date/url config options.
     This allows the user to specify/override metadata information for an input.

* include/vlc_meta.h:
   + vlc_meta_Merge( dest, src ) helper function.

* modules/demux/mp4/*:
   + Fixed a couple of mem-leaks.
   + Support for "description" metadata.