Also update unzLocateFile to the minizip-ng 4.0.4+ signature and document new unused files.

There's nothing going on with behavior here that would prevent these
from being const qualified.

Also better communicates that this function isn't intended to modify the
given resource pack.

Embrace nullptr over NULL and 0

Gets this out of the global namespace and into the Common namespace

walking the zip prevents minizip from re-reading the same
data repeatedly from the actual backing filesystem.
also improves most usages of minizip to allow for >4GB,
files altho we probably don't need it

minizip-ng is the new name used by the upstream project as well as all
distros other than Fedora (but it looks like it will be renamed there).

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.