- Lenses no longer produce light from sun at all;
artificial light is always needed.
- Grass and trees survive, don't do dual-time check.
- Breeze sounds work in twilight.
- Sponge drying only requires twilight, now also can
happen under artificial light.
- Peat to grass happens under twilight.
- No day/night cycle, no sun/moon.
- Get rid of clouds too.
- Skybox is now 100% texture-packable.
- Natural light diminishes with depth.
Night-time no longer disrupts gameplay topside, but
skylights are no longer useful to an infinite depth and
artificial light is necessary for all deep mining.
Make tree sounds managed by the mod that defines the nodes in
question using register_ambient, consistent with other things like
fluids.
nc_envsounds is now responsible for just the air moving and
cave dripping sounds made by air itself.
Common windiness logic moved into api layer.
