package/xbmc: rename to 'kodi', the new upstream project name

Background information: http://xbmc.org/introducing-kodi-14

. In a
first step to bump version to 14.0-Helix, we move the xbmc package to
a new directory called kodi.

Appropriate Config.in.legacy variables are added.

[Thomas: rename patches to the new convention.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>