fix linux buildbot

the GTK3 version check for the GDK_IS_X11_DISPLAY macro
does not appear to work well on all the machines

Change-Id: I7020afdca1b270f89910753737c2c70b61453b34

vcl/unx/gtk/window/gtksalframe.cxx

@@ -105,7 +105,7 @@
 #define IS_WIDGET_MAPPED   GTK_WIDGET_MAPPED
 #endif
 
-#if !GTK_CHECK_VERSION(3,10,0)
+#ifndef GDK_IS_X11_DISPLAY
 #define GDK_IS_X11_DISPLAY(foo) (true)
 #endif