Themes: Improve document title output.

Introduces more flexibility in filtering all parts of the document title,the
separator, and a way to short-circuit title generation. Plugins can now also
check for theme support and reliably filter the entire output. See #18548.
Deprecates `wp_title()`.

Fixes #31078.


Built from https://develop.svn.wordpress.org/trunk@35294


git-svn-id: http://core.svn.wordpress.org/trunk@35260 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/feed-rss2.php

@@ -38,7 +38,7 @@ do_action( 'rss_tag_pre', 'rss2' );
 >
 
 <channel>
-	<title><?php bloginfo_rss('name'); wp_title_rss(); ?></title>
+	<title><?php wp_title_rss(); ?></title>
 	<atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml" />
 	<link><?php bloginfo_rss('url') ?></link>
 	<description><?php bloginfo_rss("description") ?></description>