Implement fcall

[ViralBShah]

Per-Olof Persson made a great suggestion - have an fcall, like ccall, which does not require the underscores in the function name, and we can even get rid of all the ampersands. Perhaps, we can also allow specifying arrays rather than pointers in the function signatures.

[milktrader]

+1

[stevengj]

One problem is that not all Fortran compilers use the same name mangling on a given platform. The most common culprit in practice here is probably Windows, where Intel Fortran defaults to all uppercase (probably because this was the convention established on Windows by Digital Visual Fortran years ago) while gfortran uses lowercase+underscore.

[tkelman]

Yeah, ifort on Windows is kind of a pain. It's also an MSVC-style front end, so very few projects bother supporting it in their build systems. Matlab and the commercial Python distributions use it, I know that much. Not sure who else does.

Some libraries will export Fortran symbols available under multiple names to try to mitigate this. For example every function in libopenblas.dll is exported 3 times - once lowercase with trailing underscore, once lowercase without trailing underscore, and once uppercase without trailing underscore. Not all libraries are consistent about doing this, and working around it requires some occasional hacks to try to use different libraries together which were compiled with different conventions.

[ViralBShah]

Dup of #38872