minor symfony#21058 [DI] deprecate the strict attribute (xabbuh)

This PR was merged into the 3.3-dev branch.

Discussion
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[DI] deprecate the strict attribute

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | symfony#20938 (comment)
| License       | MIT
| Doc PR        |

Commits
-------

49cb4db [DI] deprecate the strict attribute

Author: fabpot

src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php

@@ -474,6 +474,10 @@ private function getArgumentsAsPhp(\DOMElement $node, $name, $lowercase = true)
 
             switch ($arg->getAttribute('type')) {
                 case 'service':
+                    if ($arg->hasAttribute('strict')) {
+                        @trigger_error(sprintf('The "strict" attribute used when referencing the "%s" service is deprecated since version 3.3 and will be removed in 4.0.', $arg->getAttribute('id')), E_USER_DEPRECATED);
+                    }
+
                     $arguments[$key] = new Reference($arg->getAttribute('id'), $invalidBehavior);
                     break;
                 case 'expression':