Rename Win32 include directory from win32_include to win32.

src/include/port/win32/sys/socket.h

@@ -0,0 +1,15 @@
+/*
+ * Unfortunately, <wingdi.h> of VC++ also defines ERROR.
+ * To avoid the conflict, we include <windows.h> here and undefine ERROR
+ * immediately.
+ *
+ * Note: Don't include <wingdi.h> directly.  It causes compile errors.
+ */
+#include <winsock2.h>
+#undef ERROR
+#undef small
+
+/* Restore old ERROR value */
+#ifdef PGERROR
+#define ERROR PGERROR
+#endif