Add support for `curl_setopt()` and `curl_multi_setopt()` with options to set callback event handlers

[mt-omarov]

The ability to set automatic event handlers via functions is needed to fully work with HTTP/2 . Particularly, support of the following options for curl_setopt():

1. CURLOPT_HEADERFUNCTION
2. CURLOPT_PASSWDFUNCTION
3. CURLOPT_PROGRESSFUNCTION
4. CURLOPT_READFUNCTION
5. CURLOPT_WRITEFUNCTION
6. CURLMOPT_PUSHFUNCTION for curl_multi_setopt().