proff_node
static void proff_node(const struct roff_node *, mandb_rec *,
proff_node(n->child, rec, roff, func);
proff_node(n->next, rec, roff, func);
proff_node(roff->first->child, rec, roff, mdocs);
proff_node(roff->first->child, rec, roff, mans);