Update libs3-dev

[László Böszörményi (GCS)]

Hi Valentin,

On Fri, Jul 10, 2015 at 9:37 PM, Valentin Libioulle
<vlibioulle at coveo.com> wrote:
> This is simply to notice you that the original git from the package
> libs3-dev was updated 3 months ago.
[...]
> The license is now LGPL v.3 instead of GPL v.3
 Thanks for the heads-up. Hopefully there will be a new release sooner
or later. At least I would not like to package a random Git snapshot
but waiting for a proper release.

Regards,
Laszlo/GCS