Support for MSVC

[ske2004]

Hi! I wanna know if MSVC support is out of the question or not. MSVC doesn't support C23 (can be worked around with clang-cl) and doesn't have some POSIX headers (like getopt.h)

[SergioFLS]

Since 76b5b13 Butterscotch now uses GNU99, which might help on getting it compiling on MSVC.

[SergioFLS]

I made my own attempt using real cl instead of clang-cl: #160