compressed files we were not passing the full wide char path to zlib, so not
all file names worked. Now we use gzopen_w available in new zlib versions.
Patch by Tamito Kajiyama, I added an extra check for the zlib version so it
keeps compiling with older versions for now.
For platform maintainers:
Part of this commit are zlib 1.2.8 libraries for windows 32 bit. We still
need update libraries for windows 64 bit and mingw. There's a readme.txt
and build.bat included with instructions on how to build.