Accept PHPUnit @dataProvider tag in unit test files

I've changed the preg_match('|^\s*\@(\w+)|', $lines[$i]) as not all tags have an extra \W after (\w+).

https://tracker.moodle.org/browse/MDL-34684?focusedCommentId=325589&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-325589