PHPDoc fixes and additions. props bananastalktome, DrewAPicture. fixes #23313.

git-svn-id: http://core.svn.wordpress.org/trunk@23365 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Select "Attribute all posts to..." radio button automatically when selecting a username from the dropdown. fixes #23224.

git-svn-id: http://core.svn.wordpress.org/trunk@23366 1a063a9b-81f0-0310-95a4-ce76da25c4cd