disable subclassing for types that aren't meant to be subclasses

[toshok]

The following list of types is "not intended for subclassing" in the UIKit notes:

• UIAlertView
• UITabBarController
• UINavigationController
• UIImagePickerController
• UIViewPrintFormatter
• UIWebView

not sure how to handle this, except perhaps by throwing an exception in the ctor when the arg list doesn't contain a handle perhaps? Actually that should work.

Auditing other class libraries is going to be a serious pain...