GDK-Win32: Avoid Redefinition of _GDK_EXTERN

Include config.h first so that _GDK_EXTERN may be defined once
and only once during the build, so that we do not get warnings/
errors for macro redefinition.

https://bugzilla.gnome.org/show_bug.cgi?id=701251

gdk/win32/gdkkeys-win32.c

@@ -21,6 +21,8 @@
  * files for a list of changes.  These files are distributed with
  * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
  */
+#include "config.h"
+
 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -36,8 +38,6 @@
 #include "gdkkeysprivate.h"
 #include "gdkwin32keys.h"
 
-#include "config.h"
-
 struct _GdkWin32KeymapClass
 {
   GdkKeymapClass parent_class;

gdk/win32/gdktestutils-win32.c

@@ -15,6 +15,8 @@
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library. If not, see <http://www.gnu.org/licenses/>.
  */
+#include "config.h"
+
 #include <gdk/gdktestutils.h>
 #include <gdk/gdkkeysyms.h>
 #include <win32/gdkwin32.h>