caca: update to newer version

Migrate to the new API instead of libcucul API, which has been merged into libcaca since 0.99.beta15:

commit f61816ceb7445f8bf818936151554ac060764b39
Author: Sam Hocevar <sam@hocevar.net>
Date:   Sat Sep 27 13:12:46 2008 +0000

Starting refactoring to get rid of libcucul. The initial reason for the
split is rendered moot by the plugin system: when enabled, binaries do
not link directly with libX11 or libGL. I hope this is a step towards
more consisteny and clarity.

It was then completely wiped out by the following commit, which is part of v0.99.beta20:

commit 5f0ec215f8c9915ed028324a8ecac8212f68e18d
Author: Sam Hocevar <sam@hocevar.net>
Date:   Thu May 3 10:33:30 2018 +0200

Remove legacy code from 10 years ago.

Note: the tarball is not yet on the FTP.