[sc34wg3] RM: built-in arc, built-in assertion, built-in node, built-in subject

[Martin Bryan]

Patrick suggested:

> TXT: built-in arc
>
> FIX: A priori arc

Please please please avoid this term. Even if it is philosophically correct
it is ugly and goes against current practice in the use of "required",
"predefined" or "built-in".

Martin Bryan