Twenty Thirteen: disable fixed navbar on small screens. Props obenland, fixes #23647.

Also closes #23526, #23535, and #23566

git-svn-id: http://core.svn.wordpress.org/trunk@23533 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Ignore protected meta keys in meta_form(). see #18786.



git-svn-id: http://core.svn.wordpress.org/trunk@23534 1a063a9b-81f0-0310-95a4-ce76da25c4cd