Revision 3135

buildsystem::var::distros: change $distros structure

The $distros variable is hash containing settings about the
distributions.

It was something like this :
$distro = {
      'cauldron' => {
         'arch' => [ 'i586', 'x86_64' ],
         'medias' => {
            'core' => [ 'release' ],
         },
         'base_medias' => [ 'core/release' ],
      },
}

It is now something like this :
$distro = {
      'cauldron' => {
         'arch' => [ 'i586', 'x86_64' ],
         'medias' => {
            'core' => {
               'repos' => {
                 'release' => {},
               },
            },
         },
         'base_medias' => [ 'core/release' ],
      },
}

This should allow setting more infos about each medias / repos, that can
be used in order to generate media.cfg config files.