Add support for OpenLDAP and 389ds PBKDF2 passwords

[olvrlrnz]

This commit enables the PAP module to recognize and handle OpenLDAP and 389ds style PBKDF2 passwords. A new password type was added that leaves the password header intact when passing it to the authentication module, because it contains the hash function used. Currently, password_process_header strips that out, as none of the other supported hash formats need it.