clash with the version hacks near the end of zlib.h

Will revisit once I know which subset of this library I actually need,
it will probably be possible to remove the entire gz* family functions.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5682 d4fa192b-c00b-0410-8231-f00ffab90ce4