This adds the sin6 case in the fhost and lhost unions and related macros.
It adds udp6_input() and udp6_output().
It adds the IPv6 case in sorecvfrom().
Finally, udp_input() is called by ip6_input().

Signed-off-by: Guillaume Subiron <maethor@subiron.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>