carla_host_control: import from pyliblo3 if available

[AdamWill]

pyliblo has not been touched upstream since 2015 and doesn't work out of the box with Python releases since 3.11. There is an actively-maintained fork called 'pyliblo3' at
https://github.com/gesellkammer/pyliblo3 which does work with current upstream Python releases. It provides a library called 'pyliblo3' rather than 'liblo'. Let's support it, and prefer it over the dead library (though the dead one will still be used if it is present and pyliblo3 is not).

[AdamWill]

I tested that, on Fedora 41 with Python 3.13 and the pyliblo3 library installed, with this patch, carla-control starts up successfully and shows its main window. I have no idea how to actually use it so can't see if there are any sneaky issues beyond that, but it's much better than the alternative (it crashes on start because we have no 'liblo' library any more).

[falkTX]

please test if it actually works.
you can just have 1 carla instance open where OSC is enabled in its settings, then start carla-control and try to add a plugin. both instances should be in sync in terms of plugins loaded, connections on the patchbay and transport info

[AdamWill]

Well I'm not really sure I'm doing it right (I only vaguely know what any of this stuff is, I'm a distro quality/Python person, not an audio engineer :>) but it seems to work, yeah.

[ahesford]

The pyliblo package is broken in more ways than one---it depends on long-deprecated and since-removed Python interfaces, and won't even build with new Cython. One way or another, this dependency has to go.

[AdamWill]

I backported this for Fedora 41 and, as I said, Carla seems to work as far as a non-specialist can test it. Haven't had any bug reports yet.