Fix build for Windows with raw MSC

[navytux]

Plain MSC defines _WIN32 but not WIN32 and this leads to build errors like this:

Z:\home\kirr\src\tools\go\pygo-win\BuildTools\vc\tools\msvc\14.35.32215\bin\Hostx64\x64\cl.exe /c /nologo /O2 /W3 /GL /DNDEBUG /
MD -DFUNCHOOK_EXPORTS -I. -I.\golang\_compat\windows -I3rdparty/funchook/include -I3rdparty/funchook/distorm/include -Ibuild\tem
p.win-amd64-cpython-310\Release\. -Ibuild\temp.win-amd64-cpython-310\. -Ibuild\lib.win-amd64-cpython-310\. -Ibuild\. -Iz:\home\k
irr\src\tools\go\pygo-win\BuildTools\vc\tools\msvc\14.35.32215\include -Iz:\home\kirr\src\tools\go\pygo-win\BuildTools\kits\10\i
nclude\10.0.22000.0\shared -Iz:\home\kirr\src\tools\go\pygo-win\BuildTools\kits\10\include\10.0.22000.0\ucrt -Iz:\home\kirr\src\
tools\go\pygo-win\BuildTools\kits\10\include\10.0.22000.0\um -Iz:\home\kirr\src\tools\go\pygo-win\BuildTools\kits\10\include\10.
0.22000.0\winrt /Tc3rdparty/funchook/src/funchook.c /Fobuild\temp.win-amd64-cpython-310\Release\3rdparty/funchook/src/funchook.obj
funchook.c
3rdparty/funchook/src/funchook.c(61): error C2065: 'PATH_MAX': undeclared identifier
3rdparty/funchook/src/funchook.c(61): error C2057: expected constant expression
3rdparty/funchook/src/funchook.c(61): error C2466: cannot allocate an array of constant size 0
3rdparty/funchook/src/funchook.c(84): fatal error C1189: #error:  unsupported OS or compiler
error: command 'Z:\\home\\kirr\\src\\tools\\go\\pygo-win\\BuildTools\\vc\\tools\\msvc\\14.35.32215\\bin\\Hostx64\\x64\\cl.exe' f
ailed with exit code 2

https://stackoverflow.com/a/74084728/9456786
https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170

also CMake on recent VisualStudio is reported not to define WIN32 as well

https://developercommunity.visualstudio.com/t/win32-not-defined/722576

-> Fix this by using _WIN32 instead of WIN32 in the sources everywhere.

P.S. Thanks a lot for funchook!

[kubo]

@navytux Thanks.

[navytux]

@kubo, thanks for applying my patch.