correct macro is _WIN32

[bvanevery]

The .h files use WIN32 but that's a depreciated macro, the correct one is _WIN32. Visual Studio 2015 documentation lists _WIN32. https://msdn.microsoft.com/en-us/library/b0084kay.aspx There's a drop-down menu for earlier compiler documentation, and you'll see that even VS .NET 2003 listed _WIN32. "Best practice" has been to use _WIN32 for the past 12 years. Other compilers all use _WIN32 nowadays but I don't have a definitive reference for that. Yes, WIN32 was used historically but somewhere along the line it was depreciated, don't know when. Yes, CMake will pass /DWIN32 by default on the compiler command line, but kNet might be consumed by a non-CMake build system.