[gtk+] win32: fix warning

[Ignacio Casal Quinteiro <icq src gnome org>]

commit ea7c509afda813bb865027b1aa6a3e5dbe1a8417
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Fri Jan 15 11:53:51 2016 -0800

    win32: fix warning

 gdk/win32/gdkselection-win32.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/win32/gdkselection-win32.c b/gdk/win32/gdkselection-win32.c
index 0f48c7d..e1beb06 100644
--- a/gdk/win32/gdkselection-win32.c
+++ b/gdk/win32/gdkselection-win32.c
@@ -849,7 +849,7 @@ _gdk_win32_display_get_selection_property (GdkDisplay *display,
   GDK_NOTE (DND, {
       gchar *type_name = gdk_atom_name (prop->type);
 
-      g_print (" %s format:%d length:%d\n", type_name, prop->format, prop->length);
+      g_print (" %s format:%d length:%"G_GSIZE_FORMAT"\n", type_name, prop->format, prop->length);
       g_free (type_name);
     });