Show which GTA:SA files are modified when a server blocks them

[Flashmyname]

Summary

When a server blocks customized GTA:SA files, the dialog now lists the game files that differ from the original copies in mta/sa.dat, instead of only telling the player to untick the setting. Client/core links minizip to read the archive, and the message is now translatable.

Motivation

The dialog only told the player to untick "Use customized GTA:SA files", leaving them to guess which of their files caused the disconnect.

Fixes #1086.

Test plan

1. Unmodified GTA:SA install: nothing is listed and the dialog is unchanged.
2. One byte changed in data/handling.cfg, size unchanged: listed.
3. One byte changed under data/maps: listed as data/maps.

Checklist

• Your code should follow the coding guidelines.
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