databases/cego: update 2.52.14 -> 2.52.17

• Added performance patch to CegoSelect::buildJoinConditions. pPred is set to checked if analyzed as complete, also if the predicate is external ( setup via setViewCond ) In the meantime, external conditions are fully handeled via CegoDistCursor
• In CegoFieldValue::toChain, for case DATETIME resulting string was corrected. In the meantime, we avoid date value construction via date/scandate function, either the required value is calculated via cast. So just the date string value is provided in the defined datetime format.
• Added datetime cast operator to convert from string value to datetime. If used, this avoids expensive real time cast operations for queries and should accelerate execution time