Patches:

- remove dompdf from phpdocx, because we already ship dompdf in the 3rdparty's root folder (see 3ae4904 and e1e3207)
- some external entity patches from https://github.com/owncloud/3rdparty/pull/74 - they should get superseeded by updating the affected libraries.
- Doctrine: fix postgres column escaping when using reserved keyword: https://github.com/doctrine/dbal/pull/627
- backported guzzlehttp/guzzle fix from 5.3.1
