FWIW shared libraries are only a thing in 4.5+. Only static libraries exist in 4.4 and before, but some users built their own shared libraries anyways.
I've been using a (now out of date) version of abi-monitor for a while now, thanks it's a useful tool to have in the background. I didn't see that you'd got a public tracker set up, would you consider tracking my library libmosquitto? I've attached the mosquitto.json and build.sh that I have been using - I wasn't sure what you'd want out of them so I've not made this a pull request.
It would be nice to also track this one: http://thrysoee.dk/editline/. It's a separate project despite having the same name, unfortunately, and conda-forge uses the latter one.
The most recent release for x264 on the tracker is from 2017. However there have been several releases this year. Would be good if this could be refreshed a bit.