DGA Mouse and shadows

[zevv]

Game runs pretty well on my Linux debian, Nvidia Quadro NVS 140M. Framerate is not to high, but setting resolution to 800x600 is very playable.

Two issues i've run into:

- Mouse jumps around, same as in penumbra. Can be fixed by setting the environment variable SDL_VIDEO_X11_DGAMOUSE to '0'

- Casted light shows weird effects. The effect can be seen in the room where with the crack in the ceiling where the light shines through, and the boxes stacked to the wall. I guess both are suppost to cast light, but instead all objectes which should be affected by this light are painted green/blueish, flashing hue when I'm moving around. Setting 'shadows' to 'off' in graphics solves this, but alas, no shadows then.

Thanks for the great demo so far!