Optional API when building gtkmm

When enable-deprecated-api is disabled, no deprecated classes or methods will be available in gtkmm. For instance, the Gtk::FileSelection dialog will not be provided, because it is replaced by Gtk::FileChooserDialog. The reference documentation contains a full list of deprecated gtkmm API.

If deprecated gtkmm API is available, the GTKMM_DISABLE_DEPRECATED macro will not be defined.

When enable-api-atk is disabled, no atkmm API will be available in gtkmm. For instance, Gtk::Widget will not inherit from Atk::Implementor.

If the atkmm API is not available, the GTKMM_ATKMM_ENABLED macro will not be defined.