new collision free hashing of ChunkID

this time the hashing function is collision free and more performant
than the original
Build zlib from sources on Windows.

Fixes #55.
Merge pull request #54 from EtlamGit/Collision-Free-Chunk-Hashing

Collision free chunk hashing
Merge pull request #56 from madmaxoft/master

Build zlib from sources on Windows.
clean-up of double zlib files

After including the zlib library sources, zlib.h and zlib.conf are two
times in the project. They should only be inside the zlib folder.
update to zlib 1.2.8

Version 1.2.8 was released on April 28, 2013.
So there is no reason to use an completely outdated version.