* Fix: apply drop checkConstraints properly which were not applied for Enum to String
* Use IF EXISTS to drop constraints
* added TODO and comment about MariaDB supporting CHECK constraints from version 10.2.1 forward compared to MySQL 5.7/8.0 parsing but ignoring CHECK constraints
* updated reference scripts for dropping constraints on enums
* trigger based history will recreate view properly and handle default value also for history view
* HistoryTriggers are generated at the end
* Reference Script
* MYSQL: lock all tables at once
Roland Praml