Merge branch '6.4' into 7.0

* 6.4:
  fix compatibility with Redis Relay 0.8.1
  use more entropy with uniqid()
  [Cache] Improve `dbindex` DSN parameter parsing
  Support for PHP-CS-Fixer's parallel runner
  use more entropy with uniqid()
  [Contracts][HttpClient] Skip tests when zlib's `ob_gzhandler()` doesn't exist

Tests/DeprecationErrorHandler/log_file.phpt

@@ -2,7 +2,7 @@
 Test DeprecationErrorHandler with log file
 --FILE--
 <?php
-$filename = tempnam(sys_get_temp_dir(), 'sf-').uniqid();
+$filename = tempnam(sys_get_temp_dir(), 'sf-').uniqid('', true);
 $k = 'SYMFONY_DEPRECATIONS_HELPER';
 putenv($k.'='.$_SERVER[$k] = $_ENV[$k] = 'logFile='.$filename);
 putenv('ANSICON');