Revert patch --- needs more generalized solution.

Revert patch --- needs more generalized solution.

> Please find a attached a small patch that adds accessor functions
> for "aclitem" so that it is not an opaque datatype.
>
> I needed these functions to browse aclitems from user land. I can load
> them when necessary, but it seems to me that these accessors for a
> backend type belong to the backend, so I submit them.
>
> Fabien Coelho