fix for missing loggerType coverage-xml in .xsd
fix for missing loggerType coverage-xml in .xsd

added missing loggerType coverage-xml to phpunit.xsd file
didiwuliu/phpunit,DonaldKellett/phpunit,Firehed/phpunit,OndraM/phpunit,luomor/phpunit,duncan3dc/phpunit,stof/phpunit,masarakki/phpunit,sebastianbergmann/phpunit,tronsha/phpunit