Generate the subSchema in cn=Aggregate

Generate the subSchema in cn=Aggregate

This reads the schema from the in-memory structure, when the magic
attributes are requested.  The code is a modified version of that used
in the ad2oLschema tool (now shared).

The schema_fsmo module handles the insertion of the generated result.

As such, this commit also removes these entries from the setup/schema.ldif

Metze's previous stub of this functionality is also removed.

Andrew Bartlett
(This used to be commit c7c32ec7b42bdf0f7b669644516438c71b364e60)