databases/cego: 2.30.12 -> 2.30.14

• Added alter table modify command just for default values. alter table t1 modify column a default 42;
• Improvement for hash calculation in CegoBufferPool::calcSegement. For a better page spreading, the segment calculation was changed to a more linear approach
• Added more cast cases to CegoField::castTo, still not completed
• Cast handling in CegoFieldValue::castTo completed. This allows an any to any value casting, except lob values and some unsupported datetime casts ( e.g. bool to datetime really makes no sense )
• Fix in CegoBufferPool::poolInfo, the spread rate calculation was not done correctly

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