Add support for zlib-ng

[demhademha]

The following has come to my attention.
Would the performance gained from zlib-ng be worth it for lrzip-next?

[pete4abw]

Probably not. Unless you used GZIP which no one does. In fact, I have never used gzip, bzip2, or lzo. It defeats the purpose of lrzip, doesn't it? If you can think of a good use case for it, it should not be difficult. But it has to be a 100% drop in.