Query writer adaptation for OCI and Oracle

Oracle identifiers don't support "__linked_by" 
Two minor adaptation for  queryRecord and DeleteRecord

There is also a bug in oci https://bugs.php.net/bug.php?id=49803 which is solved in putting 
oci8.statement_cache_size = 0 in php.ini

Other than that, everything seems to run ok .. (your tests with "LIMIT" keyword do no work in Oracle, it has to be replaced with 'ROWNUM <= limit )