Anisotropic filtering in AC game engine

[tempest]

Come on, guys. It really makes a difference (if you care about such things), and for the size of the patch, it's definitely worth it. F1 for adding this to the official code.

One small improvement: instead of

[SELECT ALL] Code:

VARP(aniso, 0, 0, 16);

use this:

[SELECT ALL] Code:

VARFP(aniso, 0, 0, 16, initwarning("texture filtering", INIT_LOAD));

so you won't have to restart AC for changes to apply.