To investigate: update unzip.cpp, zlib

[fire-eggs]

Note: this issue is likely to be moot until such time as decoding an EPUB / ZIP fails due to bugs fixed in newer code.

"unzip.cpp" is (currently) nine years old (2012)

It is based on zlib V1.1.3 which is (currently) 23 years old (1998).

May wish to upgrade zlib at least to V1.2.11 (2017).

I don't think there are any "official" updates to "unzip.cpp", but I've found one set of changes here. Some of Vladimir's changes are similar to the optimizations I've made for DarkThumbs, but not all.