Merge branch '2.8' into 3.2

* 2.8:
  Using FQ name for PHP_VERSION_ID
  [Form] Fix \IntlDateFormatter timezone parameter usage to bypass PHP bug #66323
  Harden the debugging of Twig filters and functions
  bumped Symfony version to 2.8.22
  updated VERSION for 2.8.21
  updated CHANGELOG for 2.8.21
  bumped Symfony version to 2.7.29
  updated VERSION for 2.7.28
  update CONTRIBUTORS for 2.7.28
  updated CHANGELOG for 2.7.28

Author: fabpot

Loader/AnnotationFileLoader.php

@@ -64,7 +64,7 @@ public function load($file, $type = null)
             $collection->addResource(new FileResource($path));
             $collection->addCollection($this->loader->load($class, $type));
         }
-        if (PHP_VERSION_ID >= 70000) {
+        if (\PHP_VERSION_ID >= 70000) {
             // PHP 7 memory manager will not release after token_get_all(), see https://bugs.php.net/70098
             gc_mem_caches();
         }