Be specific in term_exists error messages in wp_insert_term() as to what already exists (name, or name and slug).

props ericmann, SergeyBiryukov.
fixes #15741.

Built from https://develop.svn.wordpress.org/trunk@26544


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Twenty Fourteen: use a more specific selector for tag links.

props iamtakashi.
fixes #26358.
Built from https://develop.svn.wordpress.org/trunk@26545


git-svn-id: http://core.svn.wordpress.org/trunk@26437 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add dashicons CSS classes for easy access by plugins and themes.

props dd32.
fixes #26227.

Built from https://develop.svn.wordpress.org/trunk@26547


git-svn-id: http://core.svn.wordpress.org/trunk@26439 1a063a9b-81f0-0310-95a4-ce76da25c4cd