boost 1.76 版本及以下兼容实现：hash＜boost::asio::ip::address_v4＞、hash＜boost::asio::ip::address_v6＞、hash＜boost:

为了保证 boost 库版本的代码兼容性，这是为了在多个平台上面跨平台编译的兼容性，所以我们通常需要去兼容打上这些补丁。

namespace std {
#if BOOST_VERSION < 107600
    template <>
    struct hash<boost::asio::ip::address_v4> {
    public:
        std::size_t operator()(const boost::asio::ip::address_v4& addr) const noexcept {
            return std::hash<unsigned int>()(addr.to_uint());
        }
    };

    template <>
    struct hash<boost::asio::ip::address_v6> {
    public:
        std::size_t operator()(const boost::asio::ip::address_v6& addr) const noexcept {
            const boost::asio::ip::address_v6::bytes_type bytes = addr.to_bytes();
            std::size_t result = static_cast<std::size_t>(addr.scope_id());
            combine_4_bytes(result, &bytes[0]);
            combine_4_bytes(result, &bytes[4]);
            combine_4_bytes(result, &bytes[8]);
            combine_4_bytes(result, &bytes[12]);