TinyMCE: update to 4.0.28. Also includes https://github.com/tinymce/tinymce/commit/43fff5b45344e0101d7d75d8e3c01e9758f0d20f. Part-props avryl for the patch on #27941, fixes #28391, #27941.
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git-svn-id: http://core.svn.wordpress.org/trunk@28430 1a063a9b-81f0-0310-95a4-ce76da25c4cd