Merge branch '3.4' into 4.1

* 3.4:
  [TwigBridge] fix lowest version of symfony/form

Author: nicolas-grekas

composer.json

@@ -23,7 +23,7 @@
         "symfony/asset": "~3.4|~4.0",
         "symfony/dependency-injection": "~3.4|~4.0",
         "symfony/finder": "~3.4|~4.0",
-        "symfony/form": "^4.1.2",
+        "symfony/form": "^4.1.5",
         "symfony/http-foundation": "~3.4|~4.0",
         "symfony/http-kernel": "~3.4|~4.0",
         "symfony/polyfill-intl-icu": "~1.0",