Allow giving a callback as an allowedValue to OptionsResolver
feature #8375 [OptionsResolver] Allow giving a callback as an allowedValue to OptionsResolver (marekkalnik)

This PR was merged into the 2.5-dev branch.

Discussion
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[OptionsResolver] Allow giving a callback as an allowedValue to OptionsResolver

I recently had to use an option which was an array and could contain some one or multiple values from a list. As it could contain all possible combinations, it was not possible to validate it with a list of allowed values.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | --
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/3437

Commits
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07d1d30 Allow giving a callback as an allowedValue to OptionsResolver
update year on licenses
Merge branch '2.3' into 2.4

* 2.3:
  update year on licenses
  rundown and typo fix
  [Process] Fix #9861 : Revert TTY mode
  [Form] Update minimal requirement in composer.json
  Fix Empty translations with Qt files
  Update UPGRADE-2.3.md to account for #9388

Conflicts:
	src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorTest.php
Merge branch '2.4'

* 2.4:
  udpated LICENSE year
  update year on licenses
  rundown and typo fix
  [Process] Fix #9861 : Revert TTY mode
  [Form] Update minimal requirement in composer.json
  Fix Empty translations with Qt files
  [Console] Fixed command name guessing if an alternative is an alias.
  Update UPGRADE-2.3.md to account for #9388
  [WebProfilerBundle] Fixed profiler toolbar icons for XHTML.
  [BrowserKit] Throw exception on invalid cookie expiration timestamp
  [Propel1Bridge][ModelChoiceList] add exception message for invalid classes