/* return true if a waypoint belongs to a line */
uint8_t wp_belongs_to_line(uint8_t i, uint8_t j, uint8_t linenum, uint8_t dir);
/* return true if a waypoint belongs to a line */
uint8_t wp_belongs_to_line(uint8_t i, uint8_t j, uint8_t linenum, uint8_t dir);