Dep/zlib: Update zlib from version 1.2.7 to 1.2.8

"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"