year.sh

Generates an animation showing the top, left, front, right, back and bottom
faces of the skybox as it would appear if you faced due north at 51 degrees N
on the prime meridian at midnight, progressing through the year.

Requires:

* The starbox program to be compiled and sitting in the current directory.
* An anim/ subdirectory below the current directory with a 280*280 pixel
  "background" image in it.
* The imagemagick suite of image tools (particularly the "convert" utility)
* The gifsicle utility, to stitch all the frames into an animation. There's
  probably a way of getting imagemagick to do it, though.

Output (will land in the anim/ directory):

* The individual frames, frame0.gif to frame71.gif.
* The animation, animation.gif.