X11 based asteroids style arcade game.
Make big rocks into little ones.

This port is based on version 5.0 of xasteroids.
The following changes have been made:

 - Improved cursor-hiding.
 - Arrow keys.
 - ANSI-C cleanups.
 - Use usleep() instead of a delay loop, when available.
 - Add prototypes.
 - Reformat man page.