Inline documentation for hooks in wp-includes/feed-atom-comments.php.

Props dustyf, piontkowski, kpdesign.
Fixes #26532.

Built from https://develop.svn.wordpress.org/trunk@26863


git-svn-id: http://core.svn.wordpress.org/trunk@26749 1a063a9b-81f0-0310-95a4-ce76da25c4cd