Handle 100 continue responses proposal

[t1gor]

Attempt to fix a 100 Continue responses issue.

[t1gor]

The build fails with an error irrelent to the change:

Parse error: syntax error, unexpected ':', expecting ';' or '{' in /home/travis/build/zendframework/zend-http/vendor/doctrine/instantiator/src/Doctrine/Instantiator/Instantiator.php on line 95

[Xerkus]

Make sure next line is empty before skipping.
On a quick glance at the specification I do not see anything preventing sending more headers with 100 status code before proceeding with actual response.

Also your extracted method does too much. Extract status line parsing logic but leave the rest out of it.
I would do something like this:

list($version, $status, $reason) = $this->parseStatusLine($firstLine);
if (static::STATUS_CODE_100 === $status) {
    $next = array_shift($lines);
    if (!empty($next)) {
        // throw exception, probably
    }
    $next = array_shift($lines);
    list($version, $status, $reason) = $this->parseStatusLine($next);
}

$response->version = $version;
$response->setStatusCode($status);
$response->setReasonPhrase($reason);

[t1gor]

Changed to work without exceptions. Rebased and fixed tests.

[Xerkus]

Please revert all changes to tests.
They are using deprecated and removed methods.

[weierophinney]

I have cherry-picked the relevant commits, ensuring the changes to tests are not propagated. Merged to master for next release.