[Validator] Added ConstraintValidator::buildViolation() helper for BC with 2.4 API
Merge branch '2.5'

* 2.5:
  [Validator] Added ConstraintValidator::buildViolation() helper for BC with 2.4 API
  [Validator] Fixed LegacyValidator when only a constraint is validated

Conflicts:
	src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
	src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
	src/Symfony/Component/Validator/Constraints/RangeValidator.php