ObjectiveC 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
ObjCProtocolQualifiers. It is a non-canonical type and is canonicalized
to the underlying type with the protocol qualifiers.
rdar://
24619481
rdar://
25060179
Differential Revision: http://reviews.llvm.org/D23079
llvm-svn: 281355