Enable loading of original DOOM 3 save games.

This makes it possible to use dhwem3 as a drop-in replacement for an existing doom3 installation.
Merge pull request #75 from hurikhan/SDL2

Fix compilation with SDL2 release
fixed potential bug.
Merge pull request #86 from dotfloat/master

fixed nested for-loops using the same counter variable in d3xp's idWeapon::GetAmmoNameForNum
Fix compilation on Gentoo

For some reason Gentoo renamed zlibs OF() macro to _Z_OF
Our minizip uses OF(), so add a #define for it in case
_Z_OF is defined.

Thanks to salamanderrake for the fix
Merge pull request #76 from bk138/master

Enable loading of original DOOM 3 save games (by accepting the original game name "DOOM 3"
Fix building with Gentoo's patched zlib.
Merge pull request #88 from waldheinz/drop-minizip-of-usage

Fix building on Gentoo by providing OF() macro if necessary

.. I hope this time it works for everyone.