The source code of Minizip is no longer embedded into TDM build.
Minizip is now consumed as a third-party library (from ThirdParty/artefacts subdirectory), just like any other library.

The files minizip_extra.c and minizip_extra.h only contain additional features.
These are some functions added by either ID software or TDM team, which are not present in the official minizip distribution.
