Fixing CVEs fixed in ELA-909-1/DLA-3513-1 in (old)stable

[Utkarsh Gupta <utkarsh@freexian.com>]

Hi Adrian,

Thanks for working on tiff. I saw the ELA-909/DLA-3513 fixes a bunch
of things in buster, stretch, and jessie. Great, thanks for that.
However, https://deb.freexian.com/extended-lts/tracker/source-package/tiff
looks a bit odd to see that (old)stable are the only releases with no
fixes, can you please prep fixes for that, too, in coordination with
security team and the maintainer?

We've been trying to fix such issues and it'll be great if we can
bridge such issues. Many thanks.


- u