Thanks Hans!
I stil have to answer the question about drawing points. I have/had an
idea how to do that, but I have to work out the details. The current
code is just an example and now that textext is working again, more
clever methods can be implemented using draw_symbol(n) and then "n"
can be either used inside textext or for drawing the n-th predefined
shape.
The (solvable) "problem" with "draw point_shape[n]" is that you would
probably like to have either filled or stroked points, so it's not
enough to define the shape only.
Just an interesting link (two days old):
http://tug.ctan.org/tex-archive/macros/latex/contrib/gnuplottex/
Mojca