Make TestExample load clang in lldb with -g.
Fix cast<> expression.

cast<> takes a pointer, and works on the type-being-pointed-to. It doesn't act like standard C++ cast expressions.
Remove Sema::ObjCContainerKind::OCK_Namespace.

ObjC namespaces aren't "containers", which is the term used for "things that can contain method declarations". @namespace is the one thing that can be paired with an @end that isn't a container.