Dashboard backwards compatibility updates.
 * Restore missing wp_dashboard_rss_control() helper.
 * Restore all original 3.7 functions, deprecating many, reusing others. 
 * Rename and remove functions so as not to clash with the original dash plugin.
 * Filter cleanup/restoration.

see #25824, #26334.

Built from https://develop.svn.wordpress.org/trunk@26690


git-svn-id: http://core.svn.wordpress.org/trunk@26580 1a063a9b-81f0-0310-95a4-ce76da25c4cd