mercurial 4.6 for stretch-backports

[Philippe Pepiot <philippe.pepiot@logilab.fr>]

Hi,

Stretch has mercurial 4.0 which is quite old now, I made a backport for
mercurial 4.6 on stretch-backports, this required no changes from the
package in unstable, so it's pretty straightforward.

Here you can find my backport https://apt.logilab.fr/pool/main/m/mercurial/mercurial_4.6-2~bpo9%2B1.dsc

I'd be great to have it in stretch-backports.

Thanks!