Safe Curl opt in url.cpp

[AntoinePrv]

Using RAII to prevent leaking memory

[JohanMabille]

There is already such a handle in curl.hpp that could be used instead.

[AntoinePrv]

There are some differences:

• ~CurlHandle calls curl_slist_free_all(p_headers) which was not the case here.
• There is no CURL* raw(); which was the point here.

Overall curl.hpp seems to be intended for actually using CURL to connect to the Internet, whereas here it is only a implementation detail for parsing urls (or at least what I'm trying to move it forward)

[Klaim]

If we keep that new RAII type, please add a comment over the class to explain why this exist and how it is different from the CurlHandle, like you did here.

[JohanMabille]

• freeing the p_headers is not an issue, the pointer is null constructed so it is a noop if you don't explicitely add any header.
• curl should wrapped instead of beeing exposed through a raw accessor, thus the usage of the wrapper in curl.

Anyway, if you prefer to keep.this tony wrapper (which is not a problem asnlong as it is not exposed in any header) you need to implement proper valu semantics; the current implementation has the same issue as CurlStr regarding the destructor.

[AntoinePrv]

@JohanMabille I think keeping these wrappers is a pragmatic choice. As discussed with @Klaim, we don't really want to rely on Curl for parsing urls in the first place, so I am happy to keep this hidden and independent from the rest of the lib.