CSRF warning docs on Request::enableHttpMethodParameterOverride()

[HttpFoundation] fixed the docs so that it gives some explanation about how you are vulnerable to CSRF when you enable the httpMethodeParameterOverride
[Form] fix form handling with unconventional request methods like OPTIONS
[Config] fix filelocator with empty name
[DependencyInjection] use inheritdoc for loaders
[Validator] Fixed Regex::getHtmlPattern() to work with complex and negated patterns
enforce memcached version to be 2.1.0

The signature of the `Memcached::get()` method changed with 2.2.0.
Therefore, tests fail in Symfony when mocking `Memcached` in the
`MemcachedSessionHandlerTest` of the HttpFoundation component (see
also php-memcached-dev/php-memcached#126 and
https://bugs.php.net/bug.php?id=66331).
minor #12297 enforce memcached version to be 2.1.0 (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

enforce memcached version to be 2.1.0

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9797
| License       | MIT
| Doc PR        |

The signature of the `Memcached::get()` method changed with 2.2.0.
Therefore, tests fail in Symfony when mocking `Memcached` in the
`MemcachedSessionHandlerTest` of the HttpFoundation component (see
also php-memcached-dev/php-memcached#126 and
https://bugs.php.net/bug.php?id=66331).

Commits
-------

2ac5c86 enforce memcached version to be 2.1.0
updated CHANGELOG for 2.3.21
update CONTRIBUTORS for 2.3.21
updated VERSION for 2.3.21
bumped Symfony version to 2.3.22
Improved the phpdoc for security token classes
[Security][listener] change priority of switchuser
minor #12310 Improved the phpdoc for security token classes (stof)

This PR was merged into the 2.3 branch.

Discussion
----------

Improved the phpdoc for security token classes

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

This will avoid to have Scrutinizer complaining that we pass an array of string rather than an array of RoleInterface for instance.

Commits
-------

7b6d115 Improved the phpdoc for security token classes
bug #12313 [Security][listener] change priority of switchuser (aitboudad)

This PR was merged into the 2.3 branch.

Discussion
----------

[Security][listener] change priority of switchuser

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

Hi,
I have the following users:
  - Manager: Allowed to access to (/admin) and has a role ROLE_ALLOWED_TO_SWITCH
  - Partner: Allowed to access to (/partner)

When I attempt to switch to partner user I get "Access denied", well I think the switchuser listener must be registred before access listener.

Commits
-------

5f8047d [Security][listener] change priority of switchuser
Break infinite loop while resolving aliases
bug #12316 Break infinite loop while resolving aliases (chx)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #12316).

Discussion
----------

Break infinite loop while resolving aliases

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

Commits
-------

acbde50 Break infinite loop while resolving aliases
Remove aligned '=>' and '='
minor #12293 Remove aligned '=>' and '=' (disquedur)

This PR was squashed before being merged into the 2.3 branch (closes #12293).

Discussion
----------

Remove aligned '=>' and '='

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | [https://github.com/symfony/symfony/issues/12284]
| License       | MIT

Could you said to me if i should make an other PR for 2.5 branch.

Commits
-------

51312d3 Remove aligned '=>' and '='
[Routing] serialize the compiled route to speed things up

This also makes the CompiledRoute implement Serializable in order to:
1. make the serialization format shorter
2. have no null bytes in there, which the native serializer add for private properties, and thus would complicate saving in databases etc.
3. We should add to our symfony BC promise, that only classes that implement Serializable are ensured to be deserializable correctly with serialized representations of the class in previous symfony versions.