Inline documentation for hooks in wp-comments-post.php.

props rzen.
see #25229.


git-svn-id: https://develop.svn.wordpress.org/trunk@25249 602fd350-edb4-49c9-b593-d223f7449a82
Inline documentation for the welcome_panel hook.

props natejacobs.
see #25229.


git-svn-id: https://develop.svn.wordpress.org/trunk@25250 602fd350-edb4-49c9-b593-d223f7449a82