support executing delimiter statement without requiring query terminator

[jennifersp]

Current Dolt sql shell executes DELIMITER ;; statement as setting delimiter to ; and terminating this query. Instead it needs to set delimiter to ;;

DELIMITER ;;
CREATE TRIGGER `ins_film` AFTER INSERT ON `film` FOR EACH ROW 
  BEGIN
    INSERT INTO film_text (film_id, title, description) VALUES (new.film_id, new.title, new.description);
  END ;;
DELIMITER ;

[jennifersp]

It works when importing this through dump file. For Dolt sql shell, additional line terminator is required to execute delimiter statement.