message: Solver_add_nccl accepts any kind of Solver
diff: @@ -288,7 +288,7 @@ void Solver_add_callback(Solver<Dtype> * solver, bp::object on_start,
  }
  // Seems boost cannot call the base method directly
  -void Solver_add_nccl(SGDSolver<Dtype>* solver
  +void Solver_add_nccl(Solver<Dtype>* solver
  #ifdef USE_NCCL
  , NCCL<Dtype>* nccl
  #endif
  