[Mingw-cross-env-list] zlib

[Marcel Wysocki]

hey,
i noticed the zlib version we use is 1.2.3
which is from 2005
there is a more current version 1.2.3.4

http://ftp.de.debian.org/debian/pool/main/z/zlib/zlib_1.2.3.4.dfsg.orig.tar.gz

i honestly dont know where it originates from
but all major linux distributions use this version.
so its well-tested
it also includes a billion fixes according the the
changelog.