databases/cego: update 2.31.6 -> 2.31.7

• Fix in CegoFieldValue for fixed value handling. In case of fixed value aggregations, the specified fixed dimension should be kept. This has been done be analysing the value dimension in the CegoFieldValue:add/sub/mu/div methods. In CegoQueryHelper::prepareFieldValue, fixed values are checked now for right dimension

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