Editor: Show 'View Post' for any post the author can read.

This expands it to private posts and matches the logic in the toolbar.

props mordauk, SergeyBiryukov.
fixes #27059.

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git-svn-id: http://core.svn.wordpress.org/trunk@27327 1a063a9b-81f0-0310-95a4-ce76da25c4cd