swift234

[swift2objc] Handle protocol and protocol composition types.

These get translated as "id <MyProto>" and "id <MyProto, OtherProto>",
of course. There's special handling for protocol metatypes so that we get
"Class <MyProto>". (Objective-C doesn't have any other way to specify what
operations are available on a particular Class, so this is pretty important!)

Swift SVN r12162