Comparisons with double precision type return wrong results

Something is very wrong here (found while creating tests for #147)

```sql
create table t(d double precision);
insert into t values (8.0);
select count(*) from t where d < 8.1; -- returns 1 (correct)
set duckdb.execution = true;
select count(*) from t where d < 8.1; -- returns 0 (wrong)
```