Twenty Thirteen: second pass at RTL support and minor style.css fixes, props obenland. See #23550.

git-svn-id: http://core.svn.wordpress.org/trunk@23674 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Thirteen: gallery styles fixed to allow image thumbnails larger than 150 to align properly. Props obenland, fixes #23742.

git-svn-id: http://core.svn.wordpress.org/trunk@23675 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Thirteen: enable a JavaScript-based fix for long sidebar areas that overflow the footer. Props obenland, fixes #23557.

git-svn-id: http://core.svn.wordpress.org/trunk@23676 1a063a9b-81f0-0310-95a4-ce76da25c4cd