Fix HTTP/2 errors with cURL post

[wpdevteam]

Latest cURL update defaults to HTTP/2, but Magento's HTTP CURL Adapter is incompatible. This patch is necessary for newer server environments.

[colinmollenhour]

Can you describe how it is incompatible? Perhaps it could be made compatible rather than disabling it?

[wpdevteam]

For cURL requests, there's no need to use HTTP/2, which would cost a lot more for a single request.
And this function call does not use input param $http_ver, which is a bug.
To make it better, perhaps can base on input param to set proper protocol.

[LeeSaferite]

@wpdevteam How is Magento's HTTP curl adapter incompatible with curl selecting HTTP/2?

[wpdevteam]

@LeeSaferite I think the main issue is that input param '$http_ver' in 'public function write' of 'lib/Varien/Http/Adapter/Curl.php' does nothing and 'CURL_HTTP_VERSION_1_1' should be the default header. It has better performance and compatibility if defaulted this way.

[colinmollenhour]

Approving since Varien_Http will never support multiplexing or server push which would be the only reasons to support HTTP/2 over HTTP/1.1.

[colinmollenhour]

Oops, merged into 1.9.3.x.. Just cherry picked into 1.9.4.x.

Thanks for the PR @wpdevteam!

[simbus82]

Nice to see that i have solved this same problem in the same manner in a plugin that connect Magento to Joomla :-)
simbus82/MageBridgeCore@f95b3fb