Adds an action object to the action group. Note that this function
does not set up the accel path of the action, which can lead to problems
if a user tries to modify the accelerator of a menuitem associated with
the action. Therefore you must either set the accel path yourself with
gtk_action_set_accel_path(), or use
gtk_action_group_add_action_with_accel (..., NULL).
Adds an action object to the action group. Note that this function does not set up the accel path of the action, which can lead to problems if a user tries to modify the accelerator of a menuitem associated with the action. Therefore you must either set the accel path yourself with gtk_action_set_accel_path(), or use gtk_action_group_add_action_with_accel (..., NULL).