warnings fix

let req_modify_s and req_modrdn_s have a common portion to interoperate within slap_mods_opattrs() (ITS#5093)

(ConfigReply) for the error messages.

_db_destroy functions.

major improvement: baseline support for back-config; minor improvement: trim code to handle absence of librewrite (enable forced when slapo-rwm is configured...)

undefined mapped attribute types.