ext-sockets required since 2.8.0

[AndreKlang]

According to composer.json, ext-sockets is just a suggestion, but since 2.8.0 it is an actual requirement since constants that is defined in that extension is used, generating loads of Notices as a result.

http://php.net/manual/en/sockets.constants.php

PHP Notice:  Use of undefined constant SOCKET_EAGAIN - assumed 'SOCKET_EAGAIN' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337

Notice: Use of undefined constant SOCKET_EAGAIN - assumed 'SOCKET_EAGAIN' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337
PHP Notice:  Use of undefined constant SOCKET_EWOULDBLOCK - assumed 'SOCKET_EWOULDBLOCK' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337

Notice: Use of undefined constant SOCKET_EWOULDBLOCK - assumed 'SOCKET_EWOULDBLOCK' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337
PHP Notice:  Use of undefined constant SOCKET_EINTR - assumed 'SOCKET_EINTR' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 343

Notice: Use of undefined constant SOCKET_EINTR - assumed 'SOCKET_EINTR' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 343
PHP Notice:  Use of undefined constant SOCKET_EAGAIN - assumed 'SOCKET_EAGAIN' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337

Notice: Use of undefined constant SOCKET_EAGAIN - assumed 'SOCKET_EAGAIN' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337
PHP Notice:  Use of undefined constant SOCKET_EWOULDBLOCK - assumed 'SOCKET_EWOULDBLOCK' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337

Notice: Use of undefined constant SOCKET_EWOULDBLOCK - assumed 'SOCKET_EWOULDBLOCK' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 337
PHP Notice:  Use of undefined constant SOCKET_EINTR - assumed 'SOCKET_EINTR' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 343

Notice: Use of undefined constant SOCKET_EINTR - assumed 'SOCKET_EINTR' in /var/www/html/vendor/php-amqplib/php-amqplib/PhpAmqpLib/Wire/IO/StreamIO.php on line 343

[lukebakken]

Great, neither my environment, nor Travis CI, nor anyone testing RC1 ran into this. I'm assuming that the sockets extension is both widely available and enabled in most environments.

I can either revert #599 or move ext-sockets into here. The latter doesn't follow semver but frankly everyone should have this module at least available.

Opinions? @hairyhum @marek-obuchowicz @michaelklishin

[marek-obuchowicz]

👍 I think that introduction of socket dependency in composer.json is a good solution. Not only those constants, but also whole implementation of SocketIO depends on functions from socket extension.
So I see it more like "explicitly declare dependency that was hidden before", which would qualify as bugfix in SemVer ;)

[lukebakken]

@marek-obuchowicz thank you for chiming in, that is perfectly reasonable.

[lukebakken]

@AndreKlang please see #610

[Taluu]

This is still a BC Break. After an update from my local (which has the socket extension), it broke my installation from docker.

I don't mind adding it, but a break is still a break.

[ostrolucky]

Adding dependencies is not BC break. Don't run update in completely different environment.