A list of the functions currently called to perform special actions, including the one just added.
When some objects are garbage collected, you may require a "special action" to be performed as well.
add-special-free-action
adds a function to perform the special action. Note that the function is applied to all objects flagged for special-free-action, so the function should check for the object's type, so that it only affects relevant objects.
The functions flag-special-free-action and flag-not-special-free-action flag and unflag objects for action.