README.gnuplot updates

[Rik]

1/4/10

Ben,

Here is most of the current README.gnuplot:
---- Start ----
Octave works best with gnuplot 4.2, which is available from
http://www.gnuplot.info.

Octave now sends data over the same pipe that is used to send commands
to gnuplot.  While this avoids the problem of cluttering /tmp with
data files, it is no longer possible to use the mouse to zoom in on
plots.  This is a limitation of gnuplot, which is unable to zoom when
the data it plots is not stored in a file.  Some work has been done to
fix this problem in newer versions of gnuplot (> 4.2.2).  See for
example, this thread
---- End  ----

Two questions.  Should we be recommending version 4.4 now?  I seem to
recall there were issues that affected 4.2.5 that weren't seen in the 4.4
release.  Secondly, is the second paragraph necessary if we recommend 4.4?
 I just tried using the middle mouse button to zoom and it worked fine.

--Rik