Back compat for media_buttons_context, which is not the correct filter for...

Back compat for media_buttons_context, which is not the correct filter for adding new media buttons. If you want to add additional media buttons, use the media_buttons action instead. fixes #22559.



git-svn-id: https://core.svn.wordpress.org/trunk@22848 1a063a9b-81f0-0310-95a4-ce76da25c4cd