s3: make own defines for ldap deref types

s3: make own defines for ldap deref types

there are too many naming clashes between different ldap libs and ldb libs.
Let's simply make our own defines. The numbers are well standarized. This also
makes the default for "ldap deref" be "default" which means we won't tell the
ldap library what to do. Ѕo by default it's all up to what the server and our
libs think they should to do.