winrt: Patched to compile on Ryan's workstation. :)

I'm not sure why I needed this, but it appears to fix the build on VS2015 here.

include/SDL_platform.h

@@ -121,7 +121,12 @@
 #if defined(WIN32) || defined(_WIN32) || defined(__CYGWIN__) || defined(__MINGW32__)
 /* Try to find out if we're compiling for WinRT or non-WinRT */
 #if defined(_MSC_VER) && defined(__has_include)
-#define HAVE_WINAPIFAMILY_H __has_include(<winapifamily.h>)
+#if __has_include(<winapifamily.h>)
+#define HAVE_WINAPIFAMILY_H 1
+#else
+#define HAVE_WINAPIFAMILY_H 0
+#endif
+
 /* If _USING_V110_SDK71_ is defined it means we are using the Windows XP toolset. */
 #elif defined(_MSC_VER) && (_MSC_VER >= 1700 && !_USING_V110_SDK71_)    /* _MSC_VER == 1700 for Visual Studio 2012 */
 #define HAVE_WINAPIFAMILY_H 1