Try to fix win32 port. Now it runs both on Win32/Win64.
Win64 port currently depends on 128bits arithmetic thus it does not run on
MSVC.
Makefile now have EXCLUDE_POSIX_LIBS knob to exclude posix related library
from build.
Introduce msys PLATFORM for Makefile.detect to use MSYS's POSIX
emulation layer. It is intended for linking against MSYS tools; it is
not for embedding to Win32 applications.
- It is possible to define `strcasecmp` and
`strncasecmp` twice if `__MINGW32__` is defined.
However, the same definition is used if it's not.
Therefore, I just moved it inside of the "if-defined"
case. It removes the errors pertaining to that header.
- Additional compilation errors related to the filesystem
implementation and POSIX definitions of constants still
are brought up when compiling on Windows 10, MSYS2-mingw-w64
with gcc.
