* use column_*() methods
* remove extra arguments from single_row()
* introduce derived class WP_Post_Comments_Table for handling the post metabox comments
* use $pending_count property instead of $_comment_pending_count global
See #14579
git-svn-id: https://develop.svn.wordpress.org/trunk@15630 602fd350-edb4-49c9-b593-d223f7449a82