Include all comment css classes when outputing the rows in the Comments admin...

Include all comment css classes when outputing the rows in the Comments admin page to allow for easy customisation by plugins. Fixes #18447 props josephscott.

git-svn-id: https://core.svn.wordpress.org/trunk@18594 1a063a9b-81f0-0310-95a4-ce76da25c4cd