fixed bug in sqrt on 32-bit machines (overflow in a)
fixed bug in sqrt on 32-bit machines (overflow in a)

(see https://lists.gforge.inria.fr/pipermail/cado-nfs-discuss/2017-September/000764.html)

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs