Deprecate widget flag macros GTK_WIDGET_STATE, GTK_WIDGET_SAVED_STATE,
GTK_WIDGET_FLAGS, GTK_WIDGET_TOPLEVEL, GTK_WIDGET_NO_WINDOW and
GTK_WIDGET_COMPOSITE_CHILD.

Also deprecate the type macros GTK_WIDGET_TYPE, GTK_OBJECT_TYPE_NAME and
GTK_OBJECT_TYPE which have become redundant.

Instances of GTK_WIDGET_TOPLEVEL are replaced with gtk_widget_is_toplevel,
GTK_WIDGET_TYPE is replaced with G_OBJECT_TYPE, GTK_WIDGET_COMPOSITE_CHILD
is replaced with use of the "composite-child" property and uses of
GTK_WIDGET_NO_WINDOW are adjusted to use gtk_widget_get_has_window.

Uses of GTK_WIDGET_SAVED_STATE and GTK_WIDGET_FLAGS inside GtkWidget are
changed to direct flag usage.

Documentation is updated to refer to gtk_widget_set_has_window and
gtk_widget_get_has_window.

Gail and tests are updated as well.

Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=69872