[FrameworkBundle] fix http-foundation requirement
[Filesystem] restore ability to create broken symlinks
bug #13109 [Filesystem] restore ability to create broken symlinks (nicolas-grekas)

This PR was merged into the 2.6 branch.

Discussion
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[Filesystem] restore ability to create broken symlinks

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12793
| License       | MIT
| Doc PR        | -

Commits
-------

3101202 [Filesystem] restore ability to create broken symlinks
[FrameworkBundle] fix expression-language requirement
[FrameworkBundle] fix browserkit requirement
Merge branch '2.5' into 2.6

* 2.5:
  [FrameworkBundle] fix browserkit requirement
  [TwigBridge] fix form requirement
  [FrameworkBundle] fix http-foundation requirement
  [CssSelector] added the license of the Python library we ported to PHP
  [SecurityBundle] avoid unneeded work

Conflicts:
	src/Symfony/Bridge/Twig/composer.json
	src/Symfony/Bundle/FrameworkBundle/composer.json
	src/Symfony/Component/HttpKernel/composer.json
Merge branch '2.6' into 2.7

* 2.6:
  [FrameworkBundle] fix browserkit requirement
  [FrameworkBundle] fix expression-language requirement
  [TwigBridge] fix form requirement
  [Filesystem] restore ability to create broken symlinks
  [FrameworkBundle] fix http-foundation requirement
  [CssSelector] added the license of the Python library we ported to PHP
  [SecurityBundle] avoid unneeded work