Memory leak in qsql_oci plugin

OCI_HTYPE_TRANS, 0, 0); 

QOCIDriver::open function using local variable OCITrans* trans;

r = OCIHandleAlloc(d->env, reinterpret_cast<void **>(&d->trans), OCI_HTYPE_TRANS, 0, 0); 

but never get released. 

In an application that running threads with open/close connection to DB a memory leak can be observed. 

Solution: 

treat OCITrans* trans in the same way as the *env variable.

Put it in the QOCIDriverPrivate section and release it while closing connection.