Fixed #12600 -- Added some extra search paths for comment preview templates,...

Fixed #12600 -- Added some extra search paths for comment preview templates, allowing for naming parity with other templates in comments and admin. Thanks to hvdklauw for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12337 bcc190cf-cafb-0310-a4f2-bffc1f526a37