New comment by jnbr on void-packages repository

https://github.com/void-linux/void-packages/issues/12035#issuecomment-497365248
Comment:
It works (at least this [example](http://gnuplot.sourceforge.net/demo/rgba_lines.html))with `gnuplot-wx` and `gnuplot-qt` with terminal type respectively `wx` or `qt` and also with terminal type `pngcairo`.
I don't know why `pngcairo` is missing in `gnuplot`.