This depends on https://reviews.llvm.org/D23078
ObjC generics: Add ObjCTypeParamType in the type system.
We also need to add ObjCTypeParamTypeLoc. ObjCTypeParamType supports the
representation of "T <protocol>" where T is a type parameter. Before this,
we use TypedefType to represent the type parameter for ObjC.
ObjCTypeParamType has "ObjCTypeParamDecl *OTPDecl" and it extends from
The last patch (patch #3) will start using this new type.