Fix LDAP search on insensitive case : - Move insensitve convertion on loading config to provider loading to avoid erasing custom data. - toLower sip_attribute to make insentive checks. - Add debug logs on what attributes are sent by the server.

About locale convertion : use default application encoding set by setlocale(). Fallback to CP_APC if not found. Mark bctbx_set_default_encoding as deprecated. setLocale()  should be used instead.