[gtk+] gdkdisplay-win32.c: Define _WIN32_WINNT

[Chun-wei Fan <fanchunwei src gnome org>]

commit 718efc2f591cdd4bdf1f4bafb24f71e643ba320c
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Nov 11 20:53:41 2016 +0800

    gdkdisplay-win32.c: Define _WIN32_WINNT
    
    ... to be for Vista (0x0600) or later.  This is so that the necessary
    items in the Windows headers be activated so that the code will build
    properly on mingw-w64, and we already require Vista or later for GTK+.
    
    Thanks Ting-Wei Lan for pointing this out.
    
    See: https://bugzilla.gnome.org/show_bug.cgi?id=768081#c62

 gdk/win32/gdkdisplay-win32.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index 8cb0aa0..c701e2e 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -17,6 +17,9 @@
  */
 
 #include "config.h"
+
+#define _WIN32_WINNT 0x0600
+
 #include "gdk.h"
 #include "gdkprivate-win32.h"
 #include "gdkdisplay-win32.h"