[gtk/wip/fanc999/fontchooser.win32] gtk/gtkfontchooserwidget.c: Fix build on MinGW

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

commit 03b49802640414ecc98491135efa640051490a99
Author: Chun-wei Fan <fanc999 yahoo com tw>
Date:   Tue Jul 24 17:39:41 2018 +0800

    gtk/gtkfontchooserwidget.c: Fix build on MinGW
    
    Define _WIN32_WINNT...

 gtk/gtkfontchooserwidget.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/gtkfontchooserwidget.c b/gtk/gtkfontchooserwidget.c
index 48f9d140be..f62e9e2701 100644
--- a/gtk/gtkfontchooserwidget.c
+++ b/gtk/gtkfontchooserwidget.c
@@ -58,6 +58,7 @@
 
 #if defined(HAVE_HARFBUZZ)
 # if defined GDK_WINDOWING_WIN32
+#  define _WIN32_WINNT 0x0600
 #  define WIN32_LEAN_AND_MEAN
 #  define COBJMACROS
 #  include <windows.h>