area light effects and backpals

[Aeva]

I don't have an example offhand, but it would be neat to support backpals and area-wide tinting.

This is the command for area-wide tinting:

seteffect red, green, blue, luma;

If memory serves, r/g/b are multiplied against the room, and luma sets how dark it is, though not entirely sure. It might just be an alpha value, blending the board against a black background.

Related, but possibly the scope for another ticket:

drawoverplayer;
drawunderplayer;
drawaslight;

These would mostly just effect the z sorting, since there is no "player". "draw as light" means something should be composited after the "light" is applied rather than before.

[Aeva]

seems to work correctly, not going to bother with backpals for now. if I change my mind later, it'll be in a new ticket