Build against zlib-ng library

[vielmetti]

There is a project zlib-ng to do a faster single-threaded zlib.

There's interest in seeing how the pigz code might be sped up by incorporating code or libraries from zlib-ng, expressed at https://github.com/Dead2/zlib-ng/issues/96

Cross-linking those two ideas, here; I have not started to try to see how the build would change to use that other library.

[cieplutki]

I have tried it and it's not trivial. It works under linux, no problem, but under windows it causes segfault I tried to debug but didn't solve it yet. So if you want to use it under linux it's pretty straightforward - configure with --zlib-compat option and compile zlib-ng, then link pigz against that library and that should be it.
If you do share your impressions.

[neurolabusc]

@vielmetti please see this pigz fork for Linux and MacOS. I uses a CMake script from @ningfei that allows you to compile pigz for the System, Cloudflare or zlib-ng. My benchmark includes a shell script that will compile all three variants, and demonstrates that at the moment CloudFlare is superior. We hope to generate a pull request with the CMake version, but need to finalize the build for the Windows operating system.