Update zlib version
zlib's 1.3 version needs an extra 1 at the end (http://zlib.net/zlib-1.3.tar.gz does not exist, while http://zlib.net/zlib-1.3.1.tar.gz does).
zlib's 1.3 version needs an extra 1 at the end (http://zlib.net/zlib-1.3.tar.gz does not exist, while http://zlib.net/zlib-1.3.1.tar.gz does).