PATCH methods

[whoshuu]

As per RFC 5789. Mechanically, the data being sent up should be similar to what's being done for a PUT, even if the semantics are all not the same (PUT's are usually for whole object replacements, PATCH's are usually for partial updates to existing objects).

The curl option to set is this:

curl_easy_setopt(curl_handle, CURLOPT_CUSTOMREQUEST, "PATCH");

The documentation can probably be folded into the header PUT Requests under a more inclusive name. Testing is a bit more involved, but can be done after the main implementation and documentation, which should be easy.