anObject -
The object being added to the end of the list.
aList -
The list object the object will be appended to.
Returns:
A reference to the modified list object.
Appends a new element, containing anObject, to the
end of the list received as the aList argument. The
list is modified in the sense that it has a new element, its length
having increased by one, as reported by the length
function.
