ITS#5340 fixes:

ITS#5340 fixes:
slap_send_ldap_result() when rs->sr_flags & REP_REF_MUSTBEFREED:
- Do not return with rs->sr_ref == <freed data>, set it to NULL instead.
- Plug memory leak when op->o_domain_scope || op->o_protocol<LDAP_VERSION3.
send_ldap_response():
- Paranoia: Reset REP_MATCHED_MUSTBEFREED and REP_REF_MUSTBEFREED,
  in case the caller reuses the SlapReply without resetting the flags.