Admin cli tool for converting innodb tables to Barracuda (backport of MDL-46235)

1/ execute unit tests in all database, mysql without innodb_file_format=Barracuda and innodb_file_per_table=1 is supposed to fail with descriptive error message 2/ execute unit tests in various MySQLs and MariaDBs you may try to tweak following settings in my.cnf: innodb_file_format innodb_file_per_table 3/ ideally test both InnoDB and XtraDB via $CFG->dboptions = array('dbengine' => 'xxx'); 4/ install moodle without the patch on MySQL and try all options of the new CLI tool at admin/cli/mysql_compressed_rows.php (ideally with and without the SUPER privilege) - the script should modify the tables if DB is configured properly or if db user has SUPER priv, error message should be printed if db cannot be fixed automatically