Fixed: CURLOPT_DNS_SERVERS + Curl.duphandle in curl-helper.c

...r.c

Given a handle with `CURLOPT_DNS_SERVERS` set, a duplicate would still point to the same argument memory location, as the argument isn't set anew in `duplicateConnection(..)`. The original could be garbage collected and the space used otherwise, while the duplicate would still point to it, potentially leading to errors during `Curl.perform` on the duplicate.

I couldn't produce that exact error, although it could be shown that the argument is not copied. Therefore this error could be possible.

Greetings