Minor correction to the demos

[Dima K. <gn...@di...>]

Hi. I'm experimenting with violin plots, and just found a minor bug in
the demos.

I'm looking at

  http://gnuplot.sourceforge.net/demo/violinplot.html

The "Same data - kernel density" section plot command has "with
filledcurves above y". Shouldn't it be "above x"? I.e. we're using the x
axis as one of the boundaries of the polygon we're filling in. The next
section turns the plots 90%, so there "above y" is correct.

dima