databases/cego: update 2.33.20 -> 2.33.21

• Added further constraint check in CegoTableManager::dropObjectSynced. Primary objects just allowed to be removed, if no foreign key reference exists
• More fixes on foreign key contraint handling in CegoTableManager::checkKeyIntegrity and CegoTableManager::insertDataTable methods
• Fix in CegoTableManager::checkKeyIntegrity. The implementation of the mehod has been completly reworked, since not all violation cases have been treated.

Submitted by: Bjoern Lemke <lemke@lemke-it.com>