duplicate_node
clone_dest = duplicate_node (dfa, org_dest, constraint);
clone_dest = duplicate_node (dfa, org_dest, constraint);
clone_dest = duplicate_node (dfa, org_dest, constraint);
clone_dest = duplicate_node (dfa, org_dest, constraint);
static Idx duplicate_node (re_dfa_t *dfa, Idx org_idx, unsigned int constraint);