Apple Mac OS support

[antonysigma]

Apple/Mac systems compiles C++ app via the LLVM/Clang toolchain, which does not yet support Bessel function of the first kind. Wait for the clang support.

Refer to llvm/llvm-project#99939 for details.

Quoting the original ISO C++ proposal:

During the discussion that led to that decision, it was principally argued that these functions’ implementation would be a development hardship and maintenance burden for vendors, noting that "Users aren’t breaking down our doors clamoring for these functions."

Currently, the MicroscPSF-Cpp automatically detects the std::cyl_bessel_j function during the project configuration step; it terminates ahead of the C++ compilation stage if the function is missing:

besselj_armadillo_support/meson.build:12:4: ERROR: Problem encountered: 
Bessel function (of the first kind) does not exist in the C++ toolchain. 
Is this ISO C++17 compilant?

A full log can be found at /Users/runner/work/MicroscPSF-Cpp/MicroscPSF-Cpp/build/meson-logs/meson-log.txt