Add a local implementation of ifaddrs.h This adds a local ifaddrs implementation to be used on Bionic or other C libraries that don't come with a getifaddrs implementation. This code was written by Kenneth MacKay and is under a two-clause BSD license (copyright information in the file headers). Signed-off-by: Stéphane Graber <stgraber@ubuntu.com> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>