global controls

move compare to frontend (disabled by default, only invoked if backend doesn't provide hook); honor ITS#3472 (disclose access check); fix ITS#3521 as well (check access to hasSubordinates); fix a problem in backend_attribute() with operational attrs; add backend_access() helper

move compare to frontend (disabled by default, only invoked if backend doesn't provide hook); honor ITS#3472 (disclose access check); fix ITS#3521 as well (check access to hasSubordinates); fix a problem in backend_attribute() with operational attrs; add backend_access() helper

	#ifdef SLAP_CONTROL_AVAILABILITY_KLUDGE
for now.  Me think its still needed (at least for FRONTEND controls).

controls can be added in two passes (e.g. by backends that actually inherit their controls from someone else)

move supported controls listing at backend startup; allow supported controls to be set/mucked in between

fix dynamically registered controls check; NOTE: controls registered by global overlays don't work yet; better leave Kurt's kludge in place right now