[sqlite] Incorrect limit behavior in conjunction with offset, union all, and order by.

[Matt DeLand]

The following SQL outputs more rows than expected.  The behavior seems to
require the use of UNION ALL, ORDER BY (in the column being selected), and
an OFFSET.

Swapping the two clauses of the union also produces the wrong result,
though it's definitely necessary to order by x.

The answer is also correct if you build an index on the queried column.

Thanks for your help (and great software)!
Matt



```
drop table if exists test;
create table test ( x );
insert into test values(1);
insert into test values(2);

-- expected output: a single row
-- 1|1
--
-- actual output:
-- 1|1
-- 2|2

SELECT * FROM (
      VALUES(0,0)
  )
  UNION ALL
  SELECT * FROM (
      SELECT rowid, x FROM test ORDER BY x
  )
LIMIT 1
OFFSET 1
;


-- test again after building index

create index test_x on test(x);

-- rerun query

SELECT * FROM (
      VALUES(0,0)
  )
  UNION ALL
  SELECT * FROM (
      SELECT rowid, x FROM test ORDER BY x
  )
LIMIT 1
OFFSET 1
;

-- output as expected!

```