swift234

[PrintAsObjC] Don't forward-declare @objc enums using typedefs.

That's a C11 feature, and we can't force everyone to enable C11 just yet.
Instead, go back to the old way of using "enum Foo" to refer to @objc enums
defined in Swift. Just don't do it unilaterally for non-@objc enums.

Should unstick the buildbot.

Swift SVN r25161