patch 7.4.1749
Problem:    When using GTK 3.20 there are a few warnings.
Solution:   Use new functions when available. (Kazunobu Kuriyama)
diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index 00196eb..77e84c1 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -1842,8 +1842,13 @@
 {
     GdkWindow * const win = gtk_widget_get_window(widget);
     GdkDisplay * const dpy = gdk_window_get_display(win);
+# if GTK_CHECK_VERSION(3,20,0)
+    GdkSeat * const seat = gdk_display_get_default_seat(dpy);
+    return gdk_seat_get_pointer(seat);
+# else
     GdkDeviceManager * const mngr = gdk_display_get_device_manager(dpy);
     return gdk_device_manager_get_client_pointer(mngr);
+# endif
 }
 
     static GdkWindow *