Unrecognized keywords and statement types on 4.5.5.1

There are just the ones that I noticed.

Unrecognized keywords for REGEXP, RLIKE
Unrecognized statement type for DISTINCT on UNION DISTINCT

``` sql
SELECT 1
FROM information_schema.TABLES
WHERE 'a' REGEXP '^[a-d]'
UNION DISTINCT
SELECT 1
FROM information_schema.TABLES
WHERE 'a' RLIKE '^[a-d]';
```
