Add Alien::PGPLOT configuration probe

[zmughal]

Alien::PGPLOT can simplify the build configuration, but first these PRs in
pgplot-autotool need to be addressed:

• Add GHA CI build djerius/pgplot-autotool#2
• Use pkg-config to get x11 and xt flags djerius/pgplot-autotool#3
• GHA: Add MSYS2 build djerius/pgplot-autotool#4

[karlglazebrook]

Also

djerius/pgplot-autotool#1

because 5.3.1 includes improvements in sys_* handling. (Esp. for MacOS)

No I did not hear from Tim, but I have the tarball and can upload it here.

[mohawk2]

No I did not hear from Tim, but I have the tarball and can upload it here.

That would be great if the licence allows, but not if it doesn't! (see my note on the other issue)

[djerius]

Are we at a stage that we can merge this with the main branch?

[osascruz]

as of version 2.28 with windows 10 - strawberry 5.32.1 PDL:
it still can't find cpgplot.h which is available at :
site\lib\auto\share\dist\Alien-PGPLOT\include\pgplot\cpgplot.h

I can't make PGPLOT compile , how to do? Please help to add support for Alien::PGPLOT
Thanks !!