all-operational overlay: allows to configure part of te DIT so that requests

all-operational overlay: allows to configure part of te DIT so that requests
with requested attribute lists empty or containing "*" are expanded
to contain "+" as well, so that all operational attributes are returned.
This may be required to work around dumb clients that interrogate
the rootDSE requesting "*" and expecting operational attributes to be
returned as well.  To make it a bit more generic, it can be configured
to do the same for an arbitrary search described by an URI.  For example,

overlay		allop
allop-URI	ldap:///??sub

before any database instantiation causes all searches to return "*","+"
when ors_attrs is NULL or countains "*".