<_description>
This screen saver was removed from the XScreenSaver distribution as of
version 4.22.
A cellular automaton that is really a two-dimensional Turing machine:
as the heads ("ants") walk along the screen, they change pixel
values in their path. Then, as they pass over changed pixels, their
behavior is influenced.
https://en.wikipedia.org/wiki/Langton%27s_ant
https://en.wikipedia.org/wiki/Turing_machine
Written by David Bagley; 1997.