@evgeni sorry, I wasn't aware, I just wanted to get some people who know the project and about packaging and Autotools to take a look, since that's mostly what this PR affects. Sorry for the (now two) pings. I did see that a `libcmark` package was added [very recently](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=840727), but I just embedded it until it's widely available. Thanks for your time.