Needs identity mapping and proxy authorization support

it's value as a unique key.

note that other controls may need different access
privileges via, e.g., backend_attribute() (syncrepl?)

(at least not with a secure authentication framework).

(slapi_x_XXX is still reserved for exported functions that are not part
of the SLAPI specification)

are allocated by the plugin

stuff).

add to 'val[.<style>=<value>' ACLs special match styles for DN-valued attributes; add negated objectClass to attribute name lists for ACLs and partial replication