Issue #2387027 by kim.pepper, pfrenssen: Upgrade PHPUnit to the latest stable release

core/composer.json

core/composer.lock

core/vendor/composer/autoload_classmap.php

core/vendor/composer/include_paths.php

core/vendor/composer/installed.json

core/vendor/phpunit/phpunit/.gitignore

core/vendor/phpunit/phpunit/.travis.yml

core/vendor/phpunit/phpunit/LICENSE

core/vendor/phpunit/phpunit/README.md

core/vendor/phpunit/phpunit/build.xml

core/vendor/phpunit/phpunit/build/phar-autoload.php.in

core/vendor/phpunit/phpunit/build/travis-ci-fail.xml

core/vendor/phpunit/phpunit/composer.json

core/vendor/phpunit/phpunit/phpunit

core/vendor/phpunit/phpunit/phpunit.xml.dist

core/vendor/phpunit/phpunit/phpunit.xsd

core/vendor/phpunit/phpunit/src/Exception.php

.../vendor/phpunit/phpunit/src/Extensions/GroupTestSuite.php

core/vendor/phpunit/phpunit/src/Extensions/PhptTestCase.php

core/vendor/phpunit/phpunit/src/Extensions/PhptTestSuite.php