This update is a collection of little improvements and a significant
verhaul of hardcopy plot and export.
Hardcopy and documentation output can now be obtained using either graph
or Gnuplot. A dialog box allows choosing output formas and a few other
settings. Additional plot/export filters can be plugged in by writing a
suitable scheme module.
There's a data-export function for extracting and saving a subset of a
datafile as ascii.
The stacking/drawing order of waveforms can be changed.
Selected waveforms are now drawn in a highlighted style.
