Bug#1049413: librsvg: Update to 2.56 or later

[Jeremy Bícha]

Source: librsvg
Version: 2.54.7+dfsg-2
Severity: wishlist
X-Debbugs-CC: werdahias at riseup.net

It would be nice if we updated librsvg to 2.56 (GNOME 44 series) or
2.58 (GNOME 45 series).

But 2.56 drops the vendored Rust crate dependencies, forcing us to
either revendor librsvg or use the Debian packaged crates. That would
complicate the packaging since it would tie librsvg into the Rust GTK
transitions and other Rust library transitions. It's possible; just
not sure we want to do it.

Matthias (CC'd) did some work earlier on this; I believe there are a
few more Rust crates that would need to be packaged if we wanted to
test this more.

See also these related librsvg bugs:
https://bugs.debian.org/1017892
https://bugs.debian.org/1017906

One extra detail: my understanding is that current Ubuntu best
practice is to vendor all Rust crates used as dependencies for
libraries and apps in Ubuntu main (which includes librsvg). This is
mentioned at https://github.com/canonical/ubuntu-mir

Alternatively, we could ask the librsvg developers to revendor librsvg.

Thank you,
Jeremy Bícha