Update zlib to 1.2.8
Update zlib to 1.2.8

Update zlib to 1.2.8

# Upstream changelog

Version 1.2.8 fixes a very rare bug in decompression.

All users are encouraged to upgrade immediately.

Version 1.2.8 also has these improvements:

 * Add new inflateGetDictionary() function
 * Fix bug where gzopen() immediately followed by gzclose() would write
an empty file instead of an empty gzip stream.
 * Fix bug in gzclose() when gzwrite() runs out of memory

BansheeMediaPlayer/bockbuild,BansheeMediaPlayer/bockbuild,BansheeMediaPlayer/bockbuild