Merge branch '3.4' into 4.0

* 3.4:
  use brace-style regex delimiters
  Fixed typo RecursiveIterator -> RecursiveIteratorIterator
  [Cache] fix logic for fetching tag versions on TagAwareAdapter
  [FrameworkBundle] Use the correct service id for CachePoolPruneCommand in its compiler pass
  Hide short exception trace by default
  [Doctrine Bridge] fix priority for doctrine event listeners
  [Validator] make phpdoc of ObjectInitializerInterface interface more accurate
  [Validator] fixes phpdoc reference to an interface that was removed in Symfony 3.0

Request.php

@@ -597,7 +597,7 @@ public static function getTrustedHeaderSet()
     public static function setTrustedHosts(array $hostPatterns)
     {
         self::$trustedHostPatterns = array_map(function ($hostPattern) {
-            return sprintf('#%s#i', $hostPattern);
+            return sprintf('{%s}i', $hostPattern);
         }, $hostPatterns);
         // we need to reset trusted hosts on trusted host patterns change
         self::$trustedHosts = array();

Tests/RequestTest.php

@@ -23,6 +23,7 @@ protected function tearDown()
     {
         // reset
         Request::setTrustedProxies(array(), -1);
+        Request::setTrustedHosts(array());
     }
 
     public function testInitialize()
@@ -1924,9 +1925,15 @@ public function testTrustedHosts()
 
         $request->headers->set('host', 'subdomain.trusted.com');
         $this->assertEquals('subdomain.trusted.com', $request->getHost());
+    }
 
-        // reset request for following tests
-        Request::setTrustedHosts(array());
+    public function testSetTrustedHostsDoesNotBreakOnSpecialCharacters()
+    {
+        Request::setTrustedHosts(array('localhost(\.local){0,1}#,example.com', 'localhost'));
+
+        $request = Request::create('/');
+        $request->headers->set('host', 'localhost');
+        $this->assertSame('localhost', $request->getHost());
     }
 
     public function testFactory()