Change ObjCRuntime::LookupClass -> GetClass, and now takes the

  ObjCInterfaceDecl.

Change ObjCRuntime::GenerateMessageSendSuper to take the
  ObjCInterfaceDecl for the super class, instead of just its name.

Change EmitObjCMessageExpr to make the right runtime calls for super
  sends in class methods (i.e. a super send with the class object as
  the receiver).

llvm-svn: 54833