netbase: Use .data() instead of .c_str() on binary string

`.c_str()` is only guaranteed to return the data up to the first NUL
character.

src/netbase.cpp

@@ -259,7 +259,7 @@ bool static Socks5(string strDest, int port, SOCKET& hSocket)
     strSocks5 += strDest;
     strSocks5 += static_cast<char>((port >> 8) & 0xFF);
     strSocks5 += static_cast<char>((port >> 0) & 0xFF);
-    ret = send(hSocket, strSocks5.c_str(), strSocks5.size(), MSG_NOSIGNAL);
+    ret = send(hSocket, strSocks5.data(), strSocks5.size(), MSG_NOSIGNAL);
     if (ret != (ssize_t)strSocks5.size())
     {
         CloseSocket(hSocket);