Merge branch '2.8' into 3.4

* 2.8:
  Remove symfony/polyfill-ctype where not needed
  Use symfony/polyfill-ctype
  [Form] fixes instance variable phpdoc in FormRegistry class

Author: nicolas-grekas

composer.json

@@ -16,7 +16,8 @@
         }
     ],
     "require": {
-        "php": "^5.5.9|>=7.0.8"
+        "php": "^5.5.9|>=7.0.8",
+        "symfony/polyfill-ctype": "~1.8"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Filesystem\\": "" },