[GH-473] Fixes bug whereby orphan-removal value in XMLDriver is incorrectly parsed as true

This issue is created automatically through a Github pull request on behalf of mjphaynes:

Url: https://github.com/doctrine/doctrine2/pull/473

Message:

I realise this is very hand wavy and if you require some more information or test cases then I can see about that.

However, just to get the issue logged, as I just spent 3 hours reverse engineering the doctrine code to find this, and it may help someone else.

Basically when reading the XML mapping data from generated XML files the orphan-removal value was being incorrectly parse as 'true' when it was set to 'false' in the mapping file.

I think this is because the XML parser was parsing the attribute as an object and when it was casted a boolean this meant the value became true. To overcome this I first cast the value as a string, and then to a bool.

Let me know if you need more information.

Thanks.