message: Remove unused local variable
  It seems like that `ps` is unused, `fc::datastream` has neither lock nor mutex.
diff: @@ -79,8 +79,6 @@ namespace eosio { namespace chain {
  void fork_database::close() {
  if( my->index.size() == 0 ) return;
  - fc::datastream<size_t> ps;
  -
  auto fork_db_dat = my->datadir / config::forkdb_filename;
  std::ofstream out( fork_db_dat.generic_string().c_str(), std::ios::out | std::ios::binary | std::ofstream::trunc );
  uint32_t num_blocks_in_fork_db = my->index.size();
  