Issue #2565337 by hussainweb, joshtaylor: Upgrade to Symfony 2.7.4

core/composer.lock

core/vendor/composer/installed.json

core/vendor/symfony/browser-kit/README.md

core/vendor/symfony/class-loader/ClassMapGenerator.php

...ndor/symfony/class-loader/Tests/ClassMapGeneratorTest.php

...symfony/class-loader/Tests/Fixtures/php5.5/class_cons.php

core/vendor/symfony/console/Command/Command.php

core/vendor/symfony/console/Descriptor/JsonDescriptor.php

.../vendor/symfony/console/Descriptor/MarkdownDescriptor.php

core/vendor/symfony/console/Descriptor/TextDescriptor.php

core/vendor/symfony/console/Event/ConsoleCommandEvent.php

core/vendor/symfony/console/Helper/DebugFormatterHelper.php

core/vendor/symfony/console/Helper/QuestionHelper.php

core/vendor/symfony/console/Helper/Table.php

core/vendor/symfony/console/Logger/ConsoleLogger.php

.../vendor/symfony/console/Question/ConfirmationQuestion.php

core/vendor/symfony/console/Style/OutputStyle.php

core/vendor/symfony/console/Tests/ApplicationTest.php

core/vendor/symfony/console/Tests/Command/CommandTest.php

core/vendor/symfony/console/Tests/Fixtures/DummyOutput.php