fsockopen's error_code & error_message are nullable.

[divinity76]

tested on 8.3.4.

[lacatoire]

LGTM. In php-src ext/standard/basic_functions.stub.php line 3836, the signature is:

  function fsockopen(string $hostname, int $port = -1, &$error_code = null, &$error_message = null, ?float $timeout = null) {}                                                                            

  The error_code and error_message parameters have no explicit type but default to null. The current documentation shows int and string with = null, which is inconsistent. Changing to int|null and string|null correctly reflects that these parameters accept null as their default value.