rely on CMake's built in FindGSL.cmake (and alike)

[slayoo]

As pointed out here: https://github.com/gnudatalanguage/gdl/pull/416 CMake now ships with a FindGSL (https://gitlab.kitware.com/cmake/cmake/commit/1b28e3b28b86de40ceb6d402b6f41f30eb0c8b59) - it would be great to double check which of the local Find files can now be removed.

[MathiasMagnus]

I also noted in the suggested CMake snippet that there is also stock FindCurses.cmake as well, even as of 2.12. Naturally, it has evolved since like most find module scripts. I don't know if it wasn't enough back then, it may be smarter now.

[Csega]

@slayoo @MathiasMagnus There is also a FindHDF5.cmake (I don't know if it is good for us), and also FindImageMagick.cmake.

[maynardGK]

At some point there was a need to improve the find of a package, and remember it was cmake 2.28 or so for a long time - what cmake has lately doesn't matter, its what it had when it was at the minimum level. To find out what changes prompted the creation of new modules, use "git log" on the file in question:

$ git log CMakeModules/FindImageMagick.cmake commit 8bb487128a0663dc63fd19f7d9cf62240ec0bea4 Author: Mark Schellens [email protected] Date: Wed Oct 14 17:33:13 2015 +0000

Fixed bug #663: Skip in GetLine functions comment lines like empty li

commit 072db906c86add90d3cb980c5539c20d3bf318ab Author: Gilles Duvert [email protected] Date: Sat Jul 5 16:08:11 2014 +0000

ImageMagick comes now in different version with 16 or 8 "quantum dept

essentially). I've aligned the .cmake with current distro's cmake. Then, e necessary CXX_FLAGS that are needed to compile accordingly to the distr there are compile warnings, if not bugs).

commit 135ff2ba74adef795640db5adb9b0b6960d6c6ed Author: Alain Coulais [email protected] Date: Fri Jun 7 13:21:14 2013 +0000

change in the file provided by CMake to support local install of IM
(tested on CentOs and OSX)

[slayoo]

As seen on #752, using FindPython3 could improve user comfort likely

[slayoo]

For the record:

Ten years ago when we started to use CMake with my student Maxime, we had very few Find*.cmake files around and Maxime created most of them (10+), from scratch or templates.

Yes it is time to cleanup !

But it is time consuming to make regressions of various systems (I maintain more than 15 VMs just to check as frequently as possible two important cases : compiling with most options, and with very few options)

I would say it would have been a very topic for a student this year, but it is quite impossible to start an internship this year here due to the situation.

Originally posted by @alaingdl in https://github.com/gnudatalanguage/gdl/issues/752#issuecomment-629176425