s.delaunay
s.voronoi

use s.out.ascii|etc/s.sweep| >tmpfile ...
to generate the vector file.

should this be replaced with functions from s.geom?
at least we can use this for regression testing
of the output of s.geom. 

License for s.sweep:
       Steve  J. Fortune (1987) A Sweepline Algorithm for Voronoi
       Diagrams, Algorithmica 2, 153-174.
       Modified by:
       James Darrell McCauley, Purdue University
       (mccauley@ecn.purdue.edu) for use with GRASS.

(collected by Andreas Lange)