Method on_int64

test/basic_parser.cpp:1531–1536

                return true;
            }
            bool on_int64( std::int64_t, string_view sv, system::error_code& )
            {
                captured.append(sv.data(), sv.size());
                captured += 's';
                return true;
            }
            bool on_uint64( std::uint64_t, string_view sv, system::error_code& )
            {
                captured.append(sv.data(), sv.size());