Introduce ObjCProtocolListType type subclass.

This is used only for keeping detailed type source information for protocol references,
it should not participate in the semantics of the type system.

Its protocol list is not canonicalized.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83093 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed