Update twentyeleven/functions.php to use the new add_theme_support() calls for...

Update twentyeleven/functions.php to use the new add_theme_support() calls for backgrounds and headers. props sabreuse for initial patch. see #20265. see #20249.



git-svn-id: https://core.svn.wordpress.org/trunk@20222 1a063a9b-81f0-0310-95a4-ce76da25c4cd