Plotting graphs and charts.  For a  short  demo, please consult demo.pl;
library('demo/charts') is a gallery covering both this library and
library('plot/barchart').  Documentation for this library is in the
XPCE/Prolog Userguide.

In XPCE 5.1.3 a number of extensions have been implemented to improve
flexablity.  These are:

	* Logarithmic axis (incomplete)

	* Programmable labels along axis.
