A CxObject has to be inserted into the Commodities network before it can
process any CxMessages.  AttachCxObj() adds a CxObject to the personal
list of another CxObject.  The HotKey.c example uses it to attach its
filter to a broker.

    void AttachCxObj ( CxObj *headobj, CxObj *co);
    void InsertCxObj ( CxObj *headobj, CxObj *co, CxObj *co_pred );
    void EnqueueCxObj( CxObj *headobj, CxObj *co );
    void SetCxObjPri ( CxObj *co, long pri );
    void RemoveCxObj ( CxObj *co );

AttachCxObj() adds the CxObject to the end of headobj's personal list.
The ordering of a CxObject list determines which object gets CxMessages
first.  InsertCxObj() also inserts a CxObject, but it inserts it after
another CxObject already in the personal list (co_pred in the prototype
above).

Brokers aren't the only CxObjects with a priority.  All CxObjects have a
priority associated with them.  To change the priority of any CxObject,
use the SetCxObjPri() function.  A commodity can use the priority to keep
CxObjects in a personal list sorted by their priority.  The
commodities.library function EnqueueCxObj() inserts a CxObject into
another CxObject's personal list based on priority.

Like its name implies, the RemoveCxObj() function removes a CxObject from
a personal list.  Note that it is not necessary to remove a CxObject from
a list in order to delete it.

     HotKey.c