Add information on CVE-2019-10782/checkstyle

This did affect unstable as the incomplete fix was applied, likely as
well the one for which a DLA was released. Not (yet) buster and stretch
as the incomplete fix was not applied at all. If it's going to be fixed
in those releases via a point release the fix should be made complete.

Add note thus as well into the entry for CVE-2019-9658.