databases/cego: 2.47.29 -> 2.47.30

Fix in CegoObjectManager for alterTableObject.
If a new system page has to be allocated, this page was not linked.
This might lead to loss table objects for corresponding altering
queries. Furthermore, the ObjectManager has been cleaned up and
reduced in code size in such a way that generic create and alter
methods are now provided for all objects
( createObject and alterObject using encoding method inherited from
CegoDecodableObject ). This results in less code, since the create/alter
operations are just implemented once.