pre-release testing version of gnuplot 5.2.4

[sfeam <sf...@us...>]

I have uploaded a 5.2.4 tarball to the "testing" section of the
gnuplot files folder on SourceForge.
   
    https://sourceforge.net/projects/gnuplot/files/gnuplot/testing/
    gnuplot-5.2.4-testing.tar.gz


This release contains
- a fix for a serious regression reported against 5.2.3 (spurious
  evaluation of logscale coordinates as UNDEFINED)
- re-implementation of the "refresh" command to correct regressions in
  5.2.0 through 5.2.3
- sanity checks for several invalid command sequences found by fuzzing
- several minor bug-fixes
- two recent minor changes back-ported from the development version

Yes it's only been a month since 5.2.3 but I think the regression
in plotting logscale axes is serious enough to warrant an immediate fix.
If you want to test before/after here is a simple trigger for the error:
    set log y
    plot [1:100] x**2, 1/0

Please use the testing tarball to confirm a successful build or
report build errors.  If no problems are found I expect to make a
regular release of 5.2.4 next week.

	Ethan