Merge branch '2.3' into 2.7

* 2.3:
  [ci] Fix tests requirements

Conflicts:
	src/Symfony/Component/Validator/Tests/Mapping/Cache/LegacyApcCacheTest.php

Author: nicolas-grekas

Tests/Extension/Core/EventListener/TrimListenerTest.php

@@ -42,13 +42,10 @@ public function testTrimSkipNonStrings()
 
     /**
      * @dataProvider spaceProvider
+     * @requires extension mbstring
      */
     public function testTrimUtf8Separators($hex)
     {
-        if (!function_exists('mb_convert_encoding')) {
-            $this->markTestSkipped('The "mb_convert_encoding" function is not available');
-        }
-
         // Convert hexadecimal representation into binary
         // H: hex string, high nibble first (UCS-2BE)
         // *: repeat until end of string