This method tells an object to add itself to the end of a specified Exec
list.  Boopsi objects contain a minnode structure used for this purpose.
The return value for this method is not explicitly defined.

The method uses a custom message (defined in <intuition/classusr.h>):

    struct opAddTail {
        ULONG       MethodID;   /* OM_ADDTAIL */
        struct List *opat_List; /* The exec list to add the object to */
    };

The opat_List can be any Exec list.  Use the Intuition function
nextobject() to step through this list.