minor #12968 Deprecations (jzawadzki, dkvk, nicolas-grekas, picur, mrcmorales)

This PR was merged into the 2.7 branch.

Discussion
----------

Deprecations

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12625, #12605, #12628, #12622, #12642, #12609, #12651, #12604,  #12607, #12667, #12648
| License       | MIT
| Doc PR        | -

Cherry-picking some pending PRs to make them move forward

Commits
-------

badf8fc [Form] Log deprecation of constants, fixes #12607 #12667
1d58df4 Fix deprecation notice on VirtualFormAwareIterator
e2a19ee Add a deprecation note about VirtualFormAwareIterator
ab4d9b8 Add a deprecation note about CsrfProviderInterface
cb70632 [HttpKernel] fix deprecation notice for Kernel::init()
b5a315d [HttpKernel] Added deprecated error to init()
70012c1 [Hackday] [2.7] Add a deprecation note about TypeTestCase

Author: fabpot

Kernel.php

@@ -85,7 +85,13 @@ public function __construct($environment, $debug)
             $this->startTime = microtime(true);
         }
 
-        $this->init();
+        $defClass = new \ReflectionMethod($this, 'init');
+        $defClass = $defClass->getDeclaringClass()->name;
+
+        if (__CLASS__ !== $defClass) {
+            trigger_error(sprintf('Calling %s::init() was deprecated in Symfony 2.3 and will be removed in 3.0. Move your logic to the constructor instead.', $defClass), E_USER_DEPRECATED);
+            $this->init();
+        }
     }
 
     /**

Tests/DataCollector/ConfigDataCollectorTest.php

@@ -69,10 +69,6 @@ public function registerBundles()
     {
     }
 
-    public function init()
-    {
-    }
-
     public function getBundles()
     {
         return array();