Add c-ares library from bug #6482.
Most of the credit goes to Gennady Proskurin <gpq@mail.ru>
[Thomas: fix comment explaining why we need autoreconf.]
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
