idmap_hash: Add the idmap/nss-info provider from Likewise Open.

idmap_hash: Add the idmap/nss-info provider from Likewise Open.

* Port the Likewise Open idmap/nss_info provider (renamed to
  idmap_hash).

* uids & gids are generated based on a hashing algorithm that collapse
  the Domain SID to a 31 bit number.  The reverse mapping from the
  high order 11 bits to the originat8ing sdomain SID is stored in
  a has table initialized at start up.

* Includes support for "idmap_hash:name_map = <filename>" for the
  name aliasing layer.  The name map file consist of entries in
  the form "alias = DOMAIN\name"