add status attribute to post in all relevant api functions

Hi,

Android Apps (and other 3rd-party applications) for semantic Scuttle, like [scuttloid](https://github.com/ilesinge/scuttloid) can't access the privacy status of the bookmarks. It is needed to highlight private posts and to keep the previous privacy status when editing a bookmark.

I have added a status attribute where necessary.

The changes should not brake existing clients (tested with scuttloid), because it's just an additional attribute, that will be ignored, if not implemented. For the same reason it will stay compatible with the delicious API.

While looking at the API, I found that posts_public.php is confusing because it also returns private bookmarks of the current user. So I let it have the status attribute, too.

Thanks
David