dbm-db-doc is not working with grailsChange

Hi, I find the `dbm-db-doc` is not working with grailsChange which has sql inside:

```
grailsChange {
change {
sql.execute("insert x into y")
}
}
```

If you run the `dbm-db-doc` you will see the sql gets triggered. This generally will throw an exception which fail the `dbm-db-doc`.

Start by reproducing the issue with the shown grailsChange and sql.execute example while running dbm-db-doc. Trace how dbm-db-doc handles grailsChange blocks; done means documentation generation no longer executes the embedded SQL or fails with its exception.

Written by the indexing model from the issue text.