test for back-sql; disbled by default, requires some preparation (essentially the RDBMS and the ODBC) before being run

allow to search for "auxiliary" objectClasses (i.e. those in ldap_entry_objclasses); allow to return all objectClasses including "auxiliary"; various cleanup

Set flag for hasSubordinates and subschemaSubentry. Strip dynamic attributes
before storing entries in syncrepl.

- return server message on modification errors

frontend stuff moved into a database structure, essentially to allow overlays to be processed before database selection; passes all tests (ITS#3080)