Enable --with-rsvg flag for graphviz package

[tdguns]

I am trying to use animl library (https://github.com/parrt/animl) to visualize decision trees in Ubuntu artful and bionic. I am getting these errors while using this library:

```Warning: No loadimage plugin for "svg:cairo"```

After some googling, `svg:cairo` plugin depends on `--with-rsvg` being enabled during compilation. But in both versions of graphviz, this flag is `--without-rsvg`. Can I request this flag to be enabled, please?

On my bionic setup:
```
graphviz:
  Installed: 2.40.1-2
  Candidate: 2.40.1-2
  Version table:
 *** 2.40.1-2 500
        500 http://gb.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status
```
On artful setup, I guess the version of the graphviz is `2.36`.

[Laszlo Boszormenyi (gcs)]

This had been fixed in Debian some weeks ago with the 2.40.1-4 package version. Ubuntu needs to sync it to its archives for solving your bug report.

[Raphaël Droz (raphael-droz)]

Still not fixed as of 20.04.3 (graphviz version 2.43.0)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.