Loader: Use reinterpret_cast instead of C-style pointer casting

[ma8ma]

C言語スタイルのキャストを使っているとcppcheck 2.6.2に指摘されたため修正します。また、IPアドレスのデバッグプリントをIPv6に対応します。

参考文献
https://man7.org/linux/man-pages/man3/inet_ntop.3.html

cppcheckのレポート

src/jdlib/loader.cpp:1039:44: style: C-style pointer casting detected. C++ offers four different kinds of casts as
replacements: static_cast, const_cast, dynamic_cast and reinterpret_cast. A C-style cast could evaluate to any of
those automatically, thus it is considered safer if the programmer explicitly states which kind of cast is expected.
See also: https://www.securecoding.cert.org/confluence/display/cplusplus/EXP05-CPP.+Do+not+use+C-style+casts. [cstyleCast]
              << ", ip =" << inet_ntoa( (  ( sockaddr_in* )( res->ai_addr ) )->sin_addr ) << std::endl;
                                           ^

関連のpull request: #865