Http2 support

[staabm]

adding http2 support, as packagist.org supports it now
https://twitter.com/seldaek/status/1022179344091893760

composer will use repo.packagist.org in the future for package metadata
see composer/composer@c5fa3bd

[coveralls]

Coverage increased (+1.3%) to 81.146% when pulling 552267e on staabm:http2 into 4c52352 on hirak:master.

[coveralls]

Coverage increased (+1.8%) to 81.663% when pulling ff8aa0a on staabm:http2 into 4c52352 on hirak:master.

[staabm]

this should be ready to land

@hirak in case you have a benchmark or something like that, would be cool to run this PR thru it.

[staabm]

the build errors are packagist.org infra related, not caused by the PR

[staabm]

@hirak I dont have an idea why travis renderes those binary data in the logstream.

do you have an idea whats happing? (I tried updating dependencies with the last commit, but this seem not to be the underlying problem)

[staabm]

after making sure to only set the http2 version flag on the curl handle instead of the share/multi handles (which also make use of getCurlOptions), it seems to work now.

[staabm]

ping @hirak any open issues?

[hirak]

If this Pull Request is merged, does prestissimo stop working?
I want to check the operation in various environments.

• OpenSSL version
• nghttp2
• cURL version

[Ayesh]

I maintain a small service related to HTTP/2 at https://http2.pro. I have an open end point described at https://http2.pro/doc/API : Any request to https://http2.pro/api/v1 will return a JSON array of that connections HTTP/2 status. I guess it will help in automated tests?

Curl needs to be built with HTTP/2 or otherwise HTTP/2 support wouldn't work. Curl will fallback to HTTP/1.1 if the remote host does not support HTTP/2. In reality, it is more of "try 1.1 first, and upgrade to http/2 if possible" kind of operation. However, if HTTP/2 is not built into Curl, the constants will not be declared and will obviously throw errors.

nghttp2 and Openssl versions do not matter as long as curl is built with HTTP/2. PHP itself can have a different OpenSSL version that what Curl was built with.

I really think HTTP/2 support would be a good addition.

[staabm]

Ping @hirak

[staabm]

Ping @hirak