Fix typo and add more text to the error shown when 'wpdialogs' is not enqueued. Add 'wp_enqueue_editor' action fired when scripts and styles for the editor are being enqueued, fixes #16284
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git-svn-id: http://core.svn.wordpress.org/trunk@27854 1a063a9b-81f0-0310-95a4-ce76da25c4cd