#97 Update UnZip to 6.0

[P1h3r1e3d13]

UnZip is currently at 5.51, from 2005.
The latest is 6.0, from 2009. There's a list of improvements at that link.
I don't know enough to vouch for it personally, but Git for Windows has been shipping it (with patches) since 2014.

These packages are niche, but really needed when they're needed. I hope someone's maintaining this. If so, an update would be great. Thanks!