Fix various i18n issues on the dashboard. Limits it to posts and pages only for 3.8.

props SergeyBiryukov, dimadin.
fixes #26066.

Built from https://develop.svn.wordpress.org/trunk@26704


git-svn-id: http://core.svn.wordpress.org/trunk@26594 1a063a9b-81f0-0310-95a4-ce76da25c4cd