Add the lxqt-abi package and merge from Debian

The current fix is in https://git.launchpad.net/~tsimonq2/+git/liblxqt-fix but I've attached the git diff.

Applying this fix requires a no-change rebuild of the following packages:

 - lxqt-about
 - lxqt-panel
 - lxqt-sudo
 - lxqt-session
 - lxqt-runner
 - lxqt-powermanagement
 - lxqt-policykit
 - lxqt-openssh-askpass
 - lxqt-notificationd
 - lxqt-globalkeys
 - lxqt-config
 - lxqt-admin

As mentioned on IRC, please provide a debdiff which applies on top of either the current Debian or the Ubuntu source package.

Daniel, here you go, it's attached.

The merge from Debian as discussed on IRC would remove the liblxqt-data package, this adds it back.

This would still require a rebuild of all the packages mentioned above, right?

Correct, Daniel.

This merge probably need more discussions. I'll add some background on this:

LXQt upstream handle soname changes very badly in the past (see https://github.com/lxde/lxqt/issues/821). To adapt this, Debian choose to introduce an abi package, a virtual package to work like a soname package.

Personally, I think it's the wrong answer to the problem. IMO, we should patch upstream to set the correct soname name, or adapt the library binary (like a liblxqt0a or liblxqt1 ...). I don't think using a virtual package is a good answer, because Debian library system can handle this natively. Also, if we want to use this solution, we also need to move non .so files out the liblxqt0 binary (for soname transition). That's the reason of the creation of the liblxqt-data binary. Unfortunately, I failed to convince Debian maintainers about this.

However, this is an important divergence with Debian. If we introduce this, we will have to carry this diff probably forever, and I'm also not a fan of adding extra work for this (especially because I'll probably lack time to maintain it properly).

So, for this case, we have 2 choices:
- Diverge from Debian, but the merge needs to be modify to include the changes above, and that will need extra work on Ubuntu side for the future
- Follow Debian, and in this case we can probably sync liblxqt directly from Debian and drop the diff.

I'm fine with both options, if we are all aware of the consequences :-) (I'll also be happy to have an opinion on my change proposal, maybe others ubuntu devs will find it not necessary, so the choice will be easier :-)).

I would personally choose the second option if you are okay with it, Julien, because it means a lot less work in the long run.

But I lack experience in this situation. Daniel, do you have thoughts?

With the upcoming release the translations (reason for the data package) will be in *-l10n packages and are built from the new translation repository. So most reasons for a data package are gone. So its up to you - i would suggest to follow debian, its tested, less work and less error prone.

I now realize that Julien's approach is correct in not wanting the abi package.

Closing this bug, there's nothing else to do.