fixed output of bag values

Call json_encode with flags: JSON_UNESCAPED_SLASHES and
JSON_UNESCAPED_UNICODE
Add support for detection of Zend OPcache as an accelerator
Merge branch '2.2'

* 2.2:
  Fix default value handling for multi-value options
  [HttpKernel] truncate profiler token to 6 chars (see #7665)
  Disabled APC on Travis for PHP 5.5+ as it is not available
  [HttpFoundation] do not use server variable PATH_INFO because it is already decoded and thus symfony is fragile to double encoding of the path
  Fix download over SSL using IE < 8 and binary file response
  [Console] Fix merging of application definition, fixes #7068, replaces #7158
  [HttpKernel] fixed the Kernel when the ClassLoader component is not available (closes #7406)
  fixed output of bag values
  [Yaml] improved boolean naming ($notEOF -> !$EOF)
  [Yaml] fixed handling an empty value
  [Routing][XML Loader] Add a possibility to set a default value to null
  [Console] fixed handling of "0" input on ask
  The /e modifier for preg_replace() is deprecated in PHP 5.5; replace with preg_replace_callback()
  fixed handling of "0" input on ask
  [HttpFoundation] Fixed bug in key searching for NamespacedAttributeBag
  [Form] DateTimeToRfc3339Transformer use proper transformation exteption in reverse transformation
  Update PhpEngine.php
  [PropertyAccess] Add objectives to pluralMap
  [Security] Removed unused var
  [HttpFoundation] getClientIp is fixed.

Conflicts:
	src/Symfony/Component/Console/Tests/Command/CommandTest.php
	src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php
	src/Symfony/Component/HttpFoundation/Request.php
	src/Symfony/Component/HttpKernel/Kernel.php
merged branch Tatsh/add-zend-opcache-detection (PR #7674)

This PR was merged into the master branch.

Discussion
----------

[HttpKernel] ConfigDataCollector: Add support for new Zend OPcache accelerator

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

Related: https://github.com/symfony/symfony/pull/7670

**From original pull request:**

More information: https://github.com/zend-dev/ZendOptimizerPlus

This extension is compatible with PHP 5.2-5.5. I'm using it with 5.5 and 5.4. The PHP developers plan to include this as opposed to APC in PHP 5.5 core. http://php.net/archive/2013.php#id2013-03-21-1

This does not really have to do with Zend Optimiser+. It has to do with the newly open sourced version, Zend OPcache.

I noticed a *similar* PR here https://github.com/symfony/symfony/pull/7087 but did not like that the unit test check for accelerators was completely removed. I also do not consider it necessary to add more code just for an extension check (I would consider that 'unnecessary re-factoring'). And finally, I have no idea what the final purpose of it is. Based on its title, it seemed like at first that it was for Zend Optimizer+ (the proprietary extension: http://files.zend.com/help/Zend-Server-6/zend-server.htm#zendoptimizerplus.html) but then it sort of changed to adding support for Zend OPcache (the recently open sourced version).

This does only Zend OPcache. Tested on PHP 5.5 and PHP 5.4, including unit tests.

Based on naming scheme, I decided to name the function `hasZendOpcache` (ignoring the abbreviation as with `hasApc`) as opposed to `hasZendOpCache` or other names. Not sure if this is the 'perfect name' (it gets called in all lower-case in the twig file anyway).

Commits
-------

8e9cb3b Add support for detection of Zend OPcache as an accelerator