renderArea is implemented only with GTK-3

fixes build on SLED10 with gtk-2.8 and cairo-1.0.2

vcl/inc/unx/gtk/gtkframe.hxx

@@ -325,8 +325,9 @@ public:
     // only for gtk3 ...
     void pushIgnoreDamage();
     void popIgnoreDamage();
+#if GTK_CHECK_VERSION(3,0,0)
     void renderArea( cairo_t *cr, cairo_rectangle_t *src );
-
+#endif
     virtual ~GtkSalFrame();
 
     // SalGraphics or NULL, but two Graphics for all SalFrames