Update src/Symfony/Component/HttpFoundation/Request.php

This makes `getContentType()` work when a regular form is submitted.
[Form] Choice children can be template customized like collection
[Serializer] Added PropertyNormalizer, a new normalizer that maps an object's properties to an array
Call AuthenticationManager in AnonymousAuthenticationListener
[HttpKernel] Extract method to make callable controller in ControllerResolver

correct naming
SSI support
Disallow abstract definitions from doctrine event listener registration
[HttpFoundation] ResponseHeaderBag::clearCookie now accepts secure/httpOnly
Add missing dot at the end of an exception message
Added line feed to container alias description (text descriptor)
New service to simplify password encoding
[Form] Check if IntlDateFormatter constructor returned a valid object before using it
Added support for encoding and decoding namespaced xml (xmlns)
server:run command: provide more error information

The server:run command didn't provide many information when the executed
command exited unexpectedly. Now, the process' exit code is passed through
and an error message is displayed.
[Process] Reduce I/O load on Windows platform
[Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator
bug #11403 [Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator (takeit)

This PR was squashed before being merged into the 2.3 branch (closes #11403).

Discussion
----------

[Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11396
| License       | MIT

Commits
-------

3176f8b [Translator][FrameworkBundle] Added @ to the list of allowed chars in Translator
[Validator] Backported #11410 to 2.3: Object initializers are called only once per object
bug #11411 [Validator] Backported #11410 to 2.3: Object initializers are called only once per object (webmozart)

This PR was merged into the 2.3 branch.

Discussion
----------

[Validator] Backported #11410 to 2.3: Object initializers are called only once per object

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

Before, object initializers were called multiple times if an object was validated in different groups in the same validation run. The initializers, however, are not aware of the current validation group, so calling them more than once does not make sense.

Now, object initializers are called exactly once per validated object.

See #11410

Commits
-------

291cbf9 [Validator] Backported #11410 to 2.3: Object initializers are called only once per object
Add some tweaks to the pt_BR translations