Merge branch '3.1' into 3.2

* 3.1:
  [Filesystem] Remove extra argv in dumpFile() tests
  [DI] minor FileLoaders tests update
  [HttpKernel] Revert BC breaking change of Request::isMethodSafe()
  [DOMCrawler] Bug fixed
  [FrameworkBundle] Mark cache.default_*_provider services private
  [Process] Do feat test before enabling TTY mode
  bumped Symfony version to 3.1.8
  updated VERSION for 3.1.7
  updated CHANGELOG for 3.1.7
  bumped Symfony version to 2.8.15
  updated VERSION for 2.8.14
  updated CHANGELOG for 2.8.14
  bumped Symfony version to 2.7.22
  updated VERSION for 2.7.21
  update CONTRIBUTORS for 2.7.21
  updated CHANGELOG for 2.7.21
  Fix annotation type for $context
  [Doctrine][Form] support large integers

Author: fabpot

Crawler.php

@@ -930,7 +930,7 @@ public static function xpathLiteral($s)
             }
         }
 
-        return sprintf('concat(%s)', implode($parts, ', '));
+        return sprintf('concat(%s)', implode(', ', $parts));
     }
 
     /**