[Security] Use hash_equals for constant-time string comparison
[Security] Add more tests for StringUtils::equals
[Security] Fix usage of unexistent method in DoctrineAclCache.
minor #11822 [Security] Use hash_equals for constant-time string comparison (again) (dunglas)

This PR was merged into the 2.3 branch.

Discussion
----------

[Security] Use hash_equals for constant-time string comparison (again)

| 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

Use the `hash_equals` function (introduced in PHP 5.6) for timing attack safe string comparison when available.

Add in the DocBlock that length will leak (https://github.com/symfony/symfony/pull/11797#issuecomment-53990712).

Commits
-------

3071557 [Security] Add more tests for StringUtils::equals
03bd74b [Security] Use hash_equals for constant-time string comparison
[Security] Added more tests
Merge branch '2.3' into 2.4

* 2.3: (35 commits)
  [Form] Fix PHPDoc for builder setData methods The underlying data variable is typed as mixed whereas the methods paramers where typed as array.
  fixed CS
  [Intl] Improved bundle reader implementations
  [Console] guarded against invalid aliases
  switch before_script to before_install and script to install
  fixed typo
  [HttpFoundation] Request - URI - comment improvements
  [Security] Added more tests
  remove `service` parameter type from XSD
  [Intl] Added exception handler to command line scripts
  [Intl] Fixed a few bugs in TextBundleWriter
  [Intl] Updated icu.ini up to ICU 53
  [Intl] Removed non-working $fallback argument from ArrayAccessibleResourceBundle
  Use separated function to resolve command and related arguments
  [SwiftmailerBridge] Bump allowed versions of swiftmailer
  [FrameworkBundle] Remove invalid markup
  [Intl] Added "internal" tag to all classes under Symfony\Component\Intl\ResourceBundle
  Remove routes for removed WebProfiler actions
  [Security] Fix usage of unexistent method in DoctrineAclCache.
  backport more error information from 2.6 to 2.3
  ...

Conflicts:
	.travis.yml
	src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
	src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
	src/Symfony/Component/HttpKernel/Kernel.php
	src/Symfony/Component/Process/PhpExecutableFinder.php
Merge branch '2.4' into 2.5

* 2.4: (39 commits)
  [Form] Fix PHPDoc for builder setData methods The underlying data variable is typed as mixed whereas the methods paramers where typed as array.
  fixed CS
  [Intl] Improved bundle reader implementations
  [Console] guarded against invalid aliases
  switch before_script to before_install and script to install
  fixed typo
  [HttpFoundation] Request - URI - comment improvements
  [Validator] The ratio of the ImageValidator is rounded to two decimals now
  [Security] Added more tests
  remove `service` parameter type from XSD
  [Intl] Added exception handler to command line scripts
  [Intl] Fixed a few bugs in TextBundleWriter
  [Intl] Updated icu.ini up to ICU 53
  [Intl] Removed non-working $fallback argument from ArrayAccessibleResourceBundle
  Use separated function to resolve command and related arguments
  [SwiftmailerBridge] Bump allowed versions of swiftmailer
  [FrameworkBundle] Remove invalid markup
  [Intl] Added "internal" tag to all classes under Symfony\Component\Intl\ResourceBundle
  Remove routes for removed WebProfiler actions
  [Security] Fix usage of unexistent method in DoctrineAclCache.
  ...

Conflicts:
	.travis.yml
	src/Symfony/Bundle/FrameworkBundle/Command/ServerRunCommand.php
	src/Symfony/Component/HttpKernel/Kernel.php
	src/Symfony/Component/Process/PhpExecutableFinder.php