Fix inconsistent language in two function descriptions in wp-includes/functions.php.

Also adds correct coding standards to a code sample in `_deprecated_argument()`.

Props TobiasBg.
Fixes #26185.

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git-svn-id: http://core.svn.wordpress.org/trunk@28801 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Introduce 'rss_tag_pre' action, which fires between the xml and rss tags in a feed. 

props solarissmoke, wonderboymusic, DrewAPicture.
fixes #19017.
Built from https://develop.svn.wordpress.org/trunk@29014


git-svn-id: http://core.svn.wordpress.org/trunk@28802 1a063a9b-81f0-0310-95a4-ce76da25c4cd