When using CLOB as Column Type there is an incomplete SYS_... Index in the Table Indexes

```
1. Create a Column with Type CLOB  
2. Run scheme2ddl
3. There will be an incomplete SYS_.. Index in the Table Indexes. Which can't 
be excluded.

The SYS_.. Index should be omitted.

I'm using scheme2ddl 2.2.3

```

Original issue reported on code.google.com by `beerh...@gmail.com` on 25 Jul 2013 at 10:56
