SQL: Fix assumption that AND, OR operators are binary

We'll get ones that are nonbinary inside a query like:

```
SELECT
  CASE WHEN m1 > 1 AND m1 < 5 AND cnt > 1 THEN 'x' ELSE NULL END,
  COUNT(*)
FROM druid.foo
GROUP BY 1
```

Originally reported in https://groups.google.com/d/msg/druid-user/tPuxE_6nrHI/IaMkeOKLAAAJ.