Add libssl1.1 support

[nyetwurk]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=851084

[ObjectBoxPC]

There's a pull request for this submitted to another mirror of this code: j0sh/crtmpserver#9

I also previously submitted a patch to the Debian bug report originally linked, but I will concede that the pull request is superior. (In particular, it includes compatibility code for 1.0 and 1.1 whereas mine doesn't.)