message: Optimization for string. GH
diff: @@ -225,18 +225,19 @@ inline datastream<Stream>& operator>>(datastream<Stream>& ds, checksum256& d) {
  template<typename DataStream>
  DataStream& operator << ( DataStream& ds, const std::string& v ) {
  ds << unsigned_int( v.size() );
  - for( const auto& i : v )
  - ds << i;
  + if (v.size())
  + ds.write(v.data(), v.size());
  return ds;
  }
  template<typename DataStream>
  DataStream& operator >> ( DataStream& ds, std::string& v ) {
  - unsigned_int s;
  - ds >> s;
  - v.resize(s.value);
  - for( auto& i : v )
  - ds >> i;
  + std::vector<char> tmp;
  + ds >> tmp;
  + if( tmp.size() )
  + v = std::string(tmp.data(),tmp.data()+tmp.size());
  + else
  + v = std::string();
  return ds;
  }
  