gtk+ currently does not build with GSEAL enabled, so in an effort to remedy this I will be posting a series of patches to resolve it.  In order to keep it somewhat manageable I'll do this roughly per-widget.  This is the first, GtkWindow.

Anything that is GSEAL'd is moved into GtkWindowPrivate.  Anything that gets moved here that is depended upon elsewhere in gtk+ gets new API added.  This means that things that were in GtkWindow public struct which are not needed to build gtk+ did not receive new API in this patch, and I'm aware of that and would rather address that later and make this current effort about getting gtk+ building.

New API added:

G_CONST_RETURN gchar *gtk_window_get_wmclass_name  (GtkWindow *window);
G_CONST_RETURN gchar *gtk_window_get_wmclass_class (GtkWindow *window);
void       gtk_window_set_window_type              (GtkWindow *window,
                                                    GtkWindowType window_type);
GtkWindowType gtk_window_get_window_type           (GtkWindow *window);
GdkWindow *gtk_window_get_frame                    (GtkWindow *window);