static void remove_list_element(line **head, const line *l) {
        line *pos;
        line *prev=NULL;

        for (pos=*head; pos; pos=pos->next) {
                if (pos == l) {
                        if (*head == pos) {
                                /* remove head element */
                                *head=pos->next;
                        } else {
                                prev->next=pos->next;
                        }
                        if (pos->coords) {
                                crFree(pos->coords);
                        }
                        crFree(pos);
                        break;
                }
                prev=pos;
        }
}