I think its been around in application designer for a while, at least all 8.4x versions but I could be wrong.
It does need to be enabled through application designer: Tools > Change Control Administrator. In the system wide options check the Use Change Control Locking and Use Change Control History check boxes. As this is system wide, if you turn it on in a development environment all users will need to start locking definitions in order to modify them, so you might want to first try it out in a sandbox/play environment.
This isn't meant to be version control (even though the name suggests it). It is simply a way of tracking which developers are working on which definitions and it tracks a history of who has locked, modified and unlocked definitions which can be helpful.
Check out this article on change control for more information too.
