Issue #2504967 by hussainweb, joshtaylor, jibran, Berdir: Upgrade to Symfony 2.7.1

core/.gitignore

core/composer.lock

core/vendor/composer/installed.json

core/vendor/symfony/browser-kit/Client.php

core/vendor/symfony/browser-kit/Cookie.php

core/vendor/symfony/browser-kit/Tests/ClientTest.php

core/vendor/symfony/browser-kit/Tests/CookieTest.php

core/vendor/symfony/browser-kit/Tests/HistoryTest.php

core/vendor/symfony/class-loader/.gitignore

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

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

...vendor/symfony/class-loader/DebugUniversalClassLoader.php

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

core/vendor/symfony/console/Application.php

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

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

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

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

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

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