minor #25854 [DI] compilation perf tweak (nicolas-grekas)

This PR was merged into the 3.3 branch.

Discussion
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[DI] compilation perf tweak

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | no
| New feature?  | n
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

![image](https://user-images.githubusercontent.com/243674/35181621-94c5c10a-fdc5-11e7-83fb-c640a0ed2fa9.png)

Commits
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ad8aff4 [DI] compilation perf tweak

src/Symfony/Component/DependencyInjection/Compiler/AbstractRecursivePass.php

@@ -49,7 +49,7 @@ public function process(ContainerBuilder $container)
      */
     protected function processValue($value, $isRoot = false)
     {
-        if (is_array($value)) {
+        if (\is_array($value)) {
             foreach ($value as $k => $v) {
                 if ($isRoot) {
                     $this->currentId = $k;