[COVERITY] Fix a possible memory leak and some cosmetic changes.
[COVERITY] More leaks fixed.
Quit shipping zlib. This library is far too useful, far too widely used, and far
too important to have updated to being shipped within the extractor.
*nix users almost surely have it, Windows' users almost surely will download
just the binaries, and Windows' devs should know how to build it and should set
it within their dev environment.
Cosmetic.
Some better specification.