Insert commodity object 'co' into the list of objects connected to 'headObj' according to the priority of 'co'. (The priority of an object can be set by the function SetCxObjPri().)
INPUTS
headObj
the object to which 'co' shall be inserted.
co
a pointer to a commodity object
RESULT
If 'headObj' is NULL, the object 'co' and all objects connected to it are deleted. If 'co' is NULL and 'headObj' is a valid object, the latter's accumulated error will be adjusted to incorporate COERR_NULLATTACH.