Steps to reproduce:
1. Download MySQL 5.5.x tar.gz file and extract it somewhere
2. Use MySQL to install the database into some directory by using:
cd /path/to/MySQL
./scripts/mysql_install_db --datadir=/path/to/mysql_datadir
3. Download MariaDB 5.3.x tar.gz file and extract it somewhere
4. Start the MariaDB server with the datadir, that you installed MySQL in.
cd /path/to/MariaDB
./bin/mysqld_safe --datadir=/path/to/mysql_datadir &
5. Log into MariaDB
./bin/mysql --user=root
6. Try to execute the following command into SQL:
SET GLOBAL EVENT_SCHEDULER = ON;

Result:
You get the following error: "ERROR 1577 (HY000): Cannot proceed because system tables used by Event Scheduler were found damaged at server start".