feature symfony#17705 [TwigBridge] deprecate the boolean object support trigger (xabbuh)

This PR was merged into the 3.1-dev branch.

Discussion
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[TwigBridge] deprecate the boolean object support trigger

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

This reflects the changes done in the Yaml component in symfony#17578.

Commits
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27243c6 deprecate the boolean object support trigger

Author: fabpot

src/Symfony/Bridge/Twig/Extension/YamlExtension.php

@@ -39,7 +39,8 @@ public function encode($input, $inline = 0, $dumpObjects = false)
             $dumper = new YamlDumper();
         }
 
-        if (defined('Symfony\Component\Yaml\Yaml::DUMP_OBJECT')) {
+        if (defined('Symfony\Component\Yaml\Yaml::DUMP_OBJECT') && is_bool($dumpObjects)) {
+            @trigger_error('Passing a boolean flag to toggle object support is deprecated since version 3.1 and will be removed in 4.0. Use the Yaml::DUMP_OBJECT flag instead.', E_USER_DEPRECATED);
             $dumpObjects = (int) $dumpObjects;
         }