Make PHPUnit_Framework_TestListener implementations compatible to 4.0.

@DeepDiver1975 @schiesbn @icewind1991 et al.

Fixes
```
PHP Fatal error:  Class StartSessionListener contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (PHPUnit_Framework_TestListener::addRiskyTest) in /home/www-data/projects/owncloud/core/tests/startsessionlistener.php on line 44
```

http://phpunit.de/manual/4.0/en/extending-phpunit.html