merged branch franmomu/added_phpdoc_security_events (PR #6818)

This PR was squashed before being merged into the 2.0 branch (closes #6818).

Commits
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598ae9d [Security] PHPDoc in SecurityEvents

Discussion
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[Security] PHPDoc in SecurityEvents

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

I'm not sure about the description given.

src/Symfony/Component/Security/Http/SecurityEvents.php

@@ -13,7 +13,25 @@ namespace Symfony\Component\Security\Http;
 
 final class SecurityEvents
 {
+    /**
+     * The INTERACTIVE_LOGIN event occurs after a user is logged in
+     * interactively for authentication based on http, cookies or X509.
+     *
+     * The event listener method receives a
+     * Symfony\Component\Security\Http\Event\InteractiveLoginEvent instance.
+     *
+     * @var string
+     */
     const INTERACTIVE_LOGIN = 'security.interactive_login';
 
+    /**
+     * The SWITCH_USER event occurs before switch to another user and
+     * before exit from an already switched user.
+     *
+     * The event listener method receives a
+     * Symfony\Component\Security\Http\Event\SwitchUserEvent instance.
+     *
+     * @var string
+     */
     const SWITCH_USER = 'security.switch_user';
 }