Faster shader noise, and other noise types

It has come to my attention that the thing I’ve been calling “Perlin noise” for most of my life is actually called “fractal noise” and “Perlin noise” is something else. That’s kind of awkward.

Anyway, I’ve added two things:

• A shader implementation of fractal noise, which is considerably faster than the CPU-land implementations (20xish on my CPU and GPU combination)
• A shader implementation of actual Perlin noise, which is about as fast

Have fun! I should probably go back to working on duck games now.