Veusz update to 3.5.3

[Jeremy Sanders <jeremy@jeremysanders.net>]

Dear Science Team

It would be great if someone could have a look at the current version of 
the Veusz packaging (for version 3.5.3) and review if it is ready to upload:

https://salsa.debian.org/science-team/veusz

The existing package currently fails to build under unstable and does 
not run (see closed bug #1023185).

Thanks again

Jeremy