Merge branch '2.8' into 3.1

* 2.8:
  [FrameworkBundle] Check for class existence before is_subclass_of
  Update GroupSequence.php
  Code enhancement and cleanup
  [Form] Fix transformer tests after the ICU update
  [DI] Add anti-regression test
  Revert "minor #19689 [DI] Cleanup array_key_exists (ro0NL)"
  bumped Symfony version to 2.8.11
  updated VERSION for 2.8.10
  updated CHANGELOG for 2.8.10
  [BrowserKit] Fix cookie expiration on 32 bit systems
  bumped Symfony version to 2.7.18
  updated VERSION for 2.7.17
  update CONTRIBUTORS for 2.7.17
  updated CHANGELOG for 2.7.17
  Update misleading comment about RFC4627

Author: nicolas-grekas

DependencyInjection/AbstractDoctrineExtension.php

@@ -336,7 +336,7 @@ protected function loadCacheDriver($cacheName, $objectManagerName, array $cacheD
                 $memcacheClass = !empty($cacheDriver['class']) ? $cacheDriver['class'] : '%'.$this->getObjectManagerElementName('cache.memcache.class').'%';
                 $memcacheInstanceClass = !empty($cacheDriver['instance_class']) ? $cacheDriver['instance_class'] : '%'.$this->getObjectManagerElementName('cache.memcache_instance.class').'%';
                 $memcacheHost = !empty($cacheDriver['host']) ? $cacheDriver['host'] : '%'.$this->getObjectManagerElementName('cache.memcache_host').'%';
-                $memcachePort = !empty($cacheDriver['port']) || (isset($cacheDriver['port']) && $cacheDriver['port'] === 0)  ? $cacheDriver['port'] : '%'.$this->getObjectManagerElementName('cache.memcache_port').'%';
+                $memcachePort = !empty($cacheDriver['port']) || (isset($cacheDriver['port']) && $cacheDriver['port'] === 0) ? $cacheDriver['port'] : '%'.$this->getObjectManagerElementName('cache.memcache_port').'%';
                 $cacheDef = new Definition($memcacheClass);
                 $memcacheInstance = new Definition($memcacheInstanceClass);
                 $memcacheInstance->addMethodCall('connect', array(