In XCode 4.0 there's a newly designed Build Settings page. My problem is that I can't see how to remove a setting once I've specified it.

Example: I've changed "Versioning System" to "Apple Generic" at the target level. Afterwards I realised I should set it at the project level, and so I want to delete the target level setting. However, there's no way I can see to remove the setting -- you click on it and there's two options, neither of which is the default "not specified" empty setting. Hitting the delete key on the keyboard nothing.

The same goes for fields that accept text -- if I try to delete a setting by just deleting all the text set, it still shows that field in green, but with no text in it, and regards it as the presence of a setting.