Restore the revisions meta box for 3.6. Hidden by default as before. Can be useful for a few lingering use cases. see #24804.

Merges [24955] to the 3.6 branch.



git-svn-id: https://core.svn.wordpress.org/branches/3.6@24956 1a063a9b-81f0-0310-95a4-ce76da25c4cd