Merge branch '3.1'

* 3.1:
  fixed bad merge
  Fix PHP 7.1 related failures
  [VarDumper] Fix for 7.1
  fixed CS
  Added class existence check if is_subclass_of() fails in compiler passes
  Fix the DBAL session handler version check for Postgresql

Author: fabpot

composer.json

@@ -33,7 +33,7 @@
         "symfony/security-acl": "~2.8|~3.0",
         "symfony/stopwatch": "~2.8|~3.0",
         "symfony/console": "~2.8|~3.0",
-        "symfony/var-dumper": "~2.8|~3.0",
+        "symfony/var-dumper": "~2.8.9|~3.0.9|~3.1.3|~3.2",
         "symfony/expression-language": "~2.8|~3.0"
     },
     "suggest": {