Merge branch '2.8' into 3.4

* 2.8:
  Fix Clidumper tests
  Enable the fixer enforcing fully-qualified calls for compiler-optimized functions
  Apply fixers
  Disable the native_constant_invocation fixer until it can be scoped
  Update the list of excluded files for the CS fixer

Author: nicolas-grekas

HttpHeaderSerializer.php

@@ -39,15 +39,15 @@ public function serialize($links)
 
             $attributesParts = array('', sprintf('rel="%s"', implode(' ', $link->getRels())));
             foreach ($link->getAttributes() as $key => $value) {
-                if (is_array($value)) {
+                if (\is_array($value)) {
                     foreach ($value as $v) {
                         $attributesParts[] = sprintf('%s="%s"', $key, $v);
                     }
 
                     continue;
                 }
 
-                if (!is_bool($value)) {
+                if (!\is_bool($value)) {
                     $attributesParts[] = sprintf('%s="%s"', $key, $value);
 
                     continue;