Create a new file, platform.h, for platform-specific hacks
for MSVC, this includes defining strncasecmp to _stricmp and
strdup to _strdup, among other things like defining missing
stat macros
Change some things not supported in MSVC, like _Static_assert,
to their counterparts (in this case, static_assert)
Replace usage of VLAs with malloc and free
Update getopt_long and use the getopt implementation from musl
on Windows.
Use comments to show which functions from platform.h are being used
