message: Use emplace to avoid needless temp
diff: @@ -643,12 +643,9 @@ uint64_t apply_context::next_auth_sequence( account_name actor ) {
  void apply_context::add_ram_usage( account_name account, int64_t ram_delta ) {
  trx_context.add_ram_usage( account, ram_delta );
  - account_delta delta{account, ram_delta};
  - auto itr = _account_ram_deltas.find( delta );
  - if( itr == _account_ram_deltas.end() ) {
  - _account_ram_deltas.emplace( delta );
  - } else {
  - itr->delta += ram_delta;
  + auto p = _account_ram_deltas.emplace( account, ram_delta );
  + if( !p.second ) {
  + p.first->delta += ram_delta;
  }
  }
  