Oracle V5 compatibility: Process variables with > 2000 characters

When running the V6 engine with V5 compatibility using an oracle database, there are exceptions when a V5 process instance tries to save process variables with more then 2000 characters (V6 process instances work fine).

### Error updating database. Cause: java.sql.SQLDataException: ORA-01401: inserted value too large for column

It seems the following pull request https://github.com/Activiti/Activiti/pull/709 is not present in the module flowable5-engine (it is however present in the flowable5 branch) and therefore the engine still tries to save 2000-4000 character long process variables as a string (and not as a blob).