[new/wip] games/openxray (S.T.A.L.K.E.R.)

Hi ports@,

here is a WIP port of the OpenXRay game engine,
used by the S.T.A.L.K.E.R. series of games.

WWW: https://github.com/OpenXRay/xray-16

The linking step requires large amounts of RAM,
so before compiling, make sure you have your limits set:

$ ulimit -d $(ulimit -Hd)

4GB of RAM are not enough, but 16GB work fine.


If you want to start the game, you'll have to own a copy of
S.T.A.L.K.E.R Call of Pripyat or Clear Sky,
and you'll have to follow these steps, after installing:

https://github.com/OpenXRay/xray-16/wiki/%5BEN%5D-How-to-build-and-setup-on-Linux#game-resources

At last, run the game with `xr_3da`.
On the first start it may crash while compiling shaders.
Just re-run and it has probably fixed itself.


Any testing and feedback is very appreciated,
especially on how to simplify the pre-configure step.