directfb: fix GdkPixmap creation
directfb: fix GdkPixmap creation

Since GDK has introduced the offscreen window concept, pixmap can be
created using drawables which aren't native windows. This patch fix
this assumption.

Signed-off-by: Lionel Landwerlin <c05e47e57584a5194aa13fa9b87ac49f6ecd5024@gmail.com>

johne53/MB3Gtk-2,Unity-Technologies/gtk,Distrotech/gtk,johne53/MB3Gtk-2,Distrotech/gtk,johne53/MB3Gtk-2,Unity-Technologies/gtk,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Unity-Technologies/gtk,Unity-Technologies/gtk,Distrotech/gtk,Unity-Technologies/gtk