Merge branch '2.8' into 3.0

* 2.8:
  [PhpUnitBridge] Revert 7f62133939b1172e1c9924d211e1d315230b3be8
  bumped Symfony version to 2.3.40
  set s-maxage only if all responses are cacheable
  updated VERSION for 2.3.39
  update CONTRIBUTORS for 2.3.39
  updated CHANGELOG for 2.3.39
  Improved the "branch" row of the PR table
  [Debug] Replaced logic for detecting filesystem case sensitivity
  [Process] Wait a bit less on Windows
  Use debug member variable
  Autowiring the concrete class too - consistent with behavior of other services
  Fix typos #18090 1. PHPs session design to PHP's session design 2. Symfony HttpKernel offers to Symfony's HttpKernel offers 3. in which case it it should to in which case it should
  Fix for Isssue #18091
  replace perfom by perform
  minor #18088 Fix typo for profiler
  [Validator] Fixing inaccurate typehint in docblock
  [ci] remove token for composer now that rate limiting is off

Conflicts:
	CHANGELOG-2.3.md
	src/Symfony/Bridge/PhpUnit/composer.json

Constraint.php

@@ -69,7 +69,7 @@ abstract class Constraint
     /**
      * Returns the name of the given error code.
      *
-     * @param int $errorCode The error code
+     * @param string $errorCode The error code
      *
      * @return string The name of the error code
      *