message: reactor.Thread: Force instantiation of thread unique_ptrs.
  Those methods missing are a pita in GDB.
diff: @@ -598,3 +598,9 @@ namespace elle
  }
  }
  }
  +
  +// Instantiate those methods to ensure we can dereference thread pointers in
  +// debuggers.
  +template class std::unique_ptr<elle::reactor::Thread,
  + elle::reactor::Thread::Terminator>;
  +template class std::unique_ptr<elle::reactor::backend::Thread>;
  