[Validator] switched to apc_exists()

src/Symfony/Component/Validator/Mapping/Cache/ApcCache.php

@@ -15,10 +15,7 @@ class ApcCache implements CacheInterface
 
     public function has($class)
     {
-        $exists = false;
-        apc_fetch($this->prefix.$class, $exists);
-
-        return $exists;
+        return apc_exists($this->prefix.$class);
     }
 
     public function read($class)