Issue #1916936 by msonnabaum: Add vendored copy of phpunit.

core/composer.json

core/composer.lock

core/vendor/autoload.php

core/vendor/bin/phpunit

core/vendor/composer/autoload_classmap.php

core/vendor/composer/autoload_real.php

core/vendor/composer/include_paths.php

core/vendor/composer/installed.json

core/vendor/phpunit/php-code-coverage/.gitattributes

core/vendor/phpunit/php-code-coverage/.gitignore

core/vendor/phpunit/php-code-coverage/.travis.yml

core/vendor/phpunit/php-code-coverage/CONTRIBUTING.md

core/vendor/phpunit/php-code-coverage/ChangeLog.markdown

core/vendor/phpunit/php-code-coverage/LICENSE

core/vendor/phpunit/php-code-coverage/PHP/CodeCoverage.php

...r/phpunit/php-code-coverage/PHP/CodeCoverage/Autoload.php

...hpunit/php-code-coverage/PHP/CodeCoverage/Autoload.php.in

...dor/phpunit/php-code-coverage/PHP/CodeCoverage/Driver.php

...unit/php-code-coverage/PHP/CodeCoverage/Driver/Xdebug.php

.../phpunit/php-code-coverage/PHP/CodeCoverage/Exception.php