Removed use of non-portable _WIN32_WINNT macro.

src/config.h

@@ -19,14 +19,14 @@
 
 #	ifndef BGFX_CONFIG_RENDERER_DIRECT3D9
 #		define BGFX_CONFIG_RENDERER_DIRECT3D9 (0 \
-					| (BX_PLATFORM_WINDOWS && _WIN32_WINNT < 0x0602 /*_WIN32_WINNT_WIN8*/) \
+					| (BX_PLATFORM_WINDOWS && BX_PLATFORM_WINDOWS < 0x0602 /*_WIN32_WINNT_WIN8*/) \
 					| BX_PLATFORM_XBOX360 \
 					)
 #	endif // BGFX_CONFIG_RENDERER_DIRECT3D9
 
 #	ifndef BGFX_CONFIG_RENDERER_DIRECT3D11
 #		define BGFX_CONFIG_RENDERER_DIRECT3D11 (0 \
-					| (BX_PLATFORM_WINDOWS && _WIN32_WINNT >= 0x0602 /*_WIN32_WINNT_WIN8*/) \
+					| (BX_PLATFORM_WINDOWS && BX_PLATFORM_WINDOWS >= 0x0602 /*_WIN32_WINNT_WIN8*/) \
 					)
 #	endif // BGFX_CONFIG_RENDERER_DIRECT3D11