[2.2] Pass ESI header to subrequests
merged branch mweimerskirch/patch-13 (PR #7253)

This PR was squashed before being merged into the 2.2 branch (closes #7253).

Discussion
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[2.2] Pass ESI header to subrequests

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7252
| License       | MIT

Commits
-------

af819a7 [2.2] Pass ESI header to subrequests
Merge branch '2.2'

* 2.2:
  [Config] #7644 add tests for passing number looking attributes as strings
  [HttpFoundation][BrowserKit] fixed path when converting a cookie to a string
  [BrowserKit] removed dead code
  [HttpFoundation] fixed empty domain= in Cookie::__toString()
  fixed detection of secure cookies received over https
  [2.2] Pass ESI header to subrequests
  [Translation] removed an uneeded class property
  [Translation] removed unneeded getter/setter
  [Translator] added additional conversion for encodings other than utf-8
  fixed source messages to accept pluralized messages [Validator][translation][japanese] add messages for new validator
  fix a DI circular reference recognition bug
  [HttpFoundation] fixed the creation of sub-requests under some circumstances for IIS

Conflicts:
	src/Symfony/Component/HttpFoundation/Tests/CookieTest.php
[HttpKernel] allowed any callable to be returned by ControllerResolver::createController