Fix PHP 7.1 related failures

Author: nicolas-grekas

Tests/CrossCheckTest.php

@@ -34,7 +34,7 @@ public function testCrossCheck($fixture, $type)
         $loaderClass = 'Symfony\\Component\\DependencyInjection\\Loader\\'.ucfirst($type).'FileLoader';
         $dumperClass = 'Symfony\\Component\\DependencyInjection\\Dumper\\'.ucfirst($type).'Dumper';
 
-        $tmp = tempnam('sf_service_container', 'sf');
+        $tmp = tempnam(sys_get_temp_dir(), 'sf');
 
         file_put_contents($tmp, file_get_contents(self::$fixturesPath.'/'.$type.'/'.$fixture));
 

composer.json

@@ -19,7 +19,7 @@
         "php": ">=5.3.9"
     },
     "require-dev": {
-        "symfony/yaml": "~2.1",
+        "symfony/yaml": "~2.3.42|~2.7.14|~2.8.7",
         "symfony/config": "~2.2",
         "symfony/expression-language": "~2.6"
     },