3 - add missing functions (FIXED)
5 - review per-target error handling
7 - dn cache and cache exploitation to refine the candidate selection (?) (FIXED)
9 - review the group stuff (also in back-ldap!) (FIXED)
11 - review the attribute stuff (also in bacl-ldap)
12 note: this requires changing the acl stuff that checks "dnattr"
13 to call a backend specific function that determines what need
14 be done to retrieve the "dnattr" attribute from an entry.
16 - rework compare and bind to attempt to operate on all candidate entries
17 while checking at most one succeedes (FIXED, check bind)
19 - clear previously bound targets when the bind is repeated (FIXED)
21 - apply new logging to all the stuff (also in back-ldap)