Add configure test for __builtin_ctzl() support in compiler
Merge branch 'develop' of github.com:Dead2/zlib-ng into develop
Merge longest_match implementation from CloudFlare, authored by
Shuxin Yang in commit 31043308c3d3edfb487d2c4cbe7290bd5b63c65c at
https://github.com/cloudflare/zlib/commit/31043308c3d3edfb487d2c4cbe7290bd5b63c65c

This has been modified by me to fit into zlib-ng.