src/main/java/com/basistech/tclre/Nfa.java
void cparc(Arc oa, State from, State to) {
        newarc(oa.type, oa.co, from, to);
    }
void cparc(Arc oa, State from, State to) {
        newarc(oa.type, oa.co, from, to);
    }
cparc - allocate a new arc within an NFA, copying details from old one