Issue #1879410 by fabpot: Update Symfony dependency.

core/composer.lock

core/vendor/autoload.php

core/vendor/composer/autoload_real.php

core/vendor/composer/installed.json

...s-loader/Symfony/Component/ClassLoader/ApcClassLoader.php

...Symfony/Component/ClassLoader/ApcUniversalClassLoader.php

...loader/Symfony/Component/ClassLoader/DebugClassLoader.php

...ymfony/class-loader/Symfony/Component/ClassLoader/LICENSE

...er/Symfony/Component/ClassLoader/UniversalClassLoader.php

...oader/Symfony/Component/ClassLoader/XcacheClassLoader.php

...ection/Symfony/Component/DependencyInjection/CHANGELOG.md

...ncyInjection/Compiler/MergeExtensionConfigurationPass.php

...ependencyInjection/Compiler/PrependExtensionInterface.php

...ndencyInjection/Compiler/ResolveInvalidReferencesPass.php

...cyInjection/Compiler/ResolveParameterPlaceHoldersPass.php

...ction/Symfony/Component/DependencyInjection/Container.php

...ymfony/Component/DependencyInjection/ContainerBuilder.php

...tion/Symfony/Component/DependencyInjection/Definition.php

...ony/Component/DependencyInjection/DefinitionDecorator.php

...ymfony/Component/DependencyInjection/Dumper/PhpDumper.php