Remove hard dependency of RequestContext in AssetsExtension
Merge branch '2.5'

* 2.5:
  fix typos
  [HttpKernel] add use statement for phpdoc
  fixed DateComparator if file does not exist
  Disabled the PHPUnit self-update on Travis
  fix mustRun() in sigchild environments
  [ClassLoader] simplified phpdoc
  [ClassLoader] Add a __call() method to XcacheClassLoader
  fix some minor typos in tests
  [Yaml] fixed mapping keys containing a quoted #
  Added fixture to test parsing of hash keys ending with a space and #
  [Validator] Pass strict argument into the strict email validator
  [Filesystem Component] mkdir race condition fix #11626
  [Validator] reverted permissions change on translation files
  Fixed Factory services not within the ServiceReferenceGraph.
  [CssSelector] Fix URL to SimonSapin/cssselect repo
  [Validator] Fixed wrong translation keys/messages for Collection constraint. The error messages for a missing field and an unexpected field did not match the Contraint class
  Remove hard dependency of RequestContext in AssetsExtension
  added useful reminder about form.vars.errors into UPGRADE-2.5 notes
  [YAML] resolve variables in inlined YAML
  Disallow abstract definitions from doctrine event listener registration

Conflicts:
	src/Symfony/Component/Yaml/Inline.php
	src/Symfony/Component/Yaml/Parser.php
	src/Symfony/Component/Yaml/Tests/InlineTest.php