DuckDB output format

[julianhyde]

DuckDB has a nice output format (which it calls 'duckbox mode') that uses Unicode 'box drawing' characters. Example:

!set outputformat mysql
SELECT deptno, ename FROM Emp WHERE ename = 'SCOTT';
+--------+-------+
| deptno | ename |
+--------+-------+
|     20 | SCOTT |
+--------+-------+
(1 row)

!ok

!set outputformat duckbox
SELECT deptno, ename FROM Emp WHERE ename = 'SCOTT';
┌────────┬───────┐
│ deptno │ ename │
├────────┼───────┤
│     20 │ SCOTT │
└────────┴───────┘
!ok

This change would add support for !set outputformat duckbox.