user configurable root DSE attributes

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

I'd like to add support for user configurable root
DSE attributes.  That is, I'd like to be able to,
via slapd.conf, specify a set of attribute types/values
to be included in root DSE searches.

# Load LDIF as initial rootDSE entry, to be
# augmented dynamically.
rootDSE rootDSE.ldif

The attribute types and values should be schema checked, so
these directives would have to come after schema import.
The entry would be required to be oc OpenLDAProotDSE +
extensibleObject.

Basically, the code would build a static Entry *rootDSE.
Then, upon search (or compare), dynamic values would be
added before sending the response.  (yes, one could think
about allowing updates as well and writing back the ldif...
but that's a later project...  as well as using same
technics on subschema subentries).

Anyways, I don't have time at the moment to implement this.
Though someone else might like to give it a go.  Please
coordinate on devel list to avoid duplication of work.