curl-win32.h: Enable Unix Domain Sockets based on the Windows SDK version

Microsoft added support for Unix Domain Sockets in Windows 10 1803
(RS4). Rather than expect the user to enable Unix Domain Sockets by
uncommenting the #define that was added in 0fd6221f we use the RS4
pre-processor variable that is present in newer versions of the
Windows SDK.

Closes #3939

diff --git a/lib/config-win32.h b/lib/config-win32.h
index 08cfd0d4cb9d9571134acdab3b4b015a324d7a05..14bd084fe6aad13fc767ecdca51df7a4fb3a90ce 100644 (file)
--- a/lib/config-win32.h
+++ b/lib/config-win32.h
@@ -727,8 +727,12 @@ Vista
 #define USE_WIN32_CRYPTO
 
 /* Define to use Unix sockets. */
-#if defined(_MSC_VER) && _MSC_VER >= 1900
-/* #define USE_UNIX_SOCKETS */
+#if defined(_MSC_VER) && (_MSC_VER >= 1500)
+/* sdkddkver.h first shipped with Platform SDK v6.0A included with VS2008 */
+#include <sdkddkver.h>
+#if defined(NTDDI_WIN10_RS4)
+#define USE_UNIX_SOCKETS
+#endif
 #endif
 
 /* ---------------------------------------------------------------- */