[pkg-ntp-maintainers] Bug#793837: Adding tracking bug for stretch-pu

[Bernhard Schmidt]

Control: block 793837 by 868756

I have filed a pre-approval question to the SRM to update the ntp
package in Stretch to include sntp. They are not completely against it,
see #868756.

The relevant code is now in
https://anonscm.debian.org/git/pkg-ntp/pkg-ntp.git/log/?h=stretch. I
will test it some more (all the upgrade paths) and then submit the diff
to the SRMs for approval.

Bernhard