winbindd: Add support for name aliasing.

winbindd: Add support for name aliasing.

* Add support user and group name aliasing by expanding
  the ws_name_replace() and ws_name_return() functions.
  The lookup path is
     aliases -> qualified name -> SID
     SID -> fully qualified name -> alias
  In other words, the name aliasing support is a thin layer
  built on top of SID/NAME translation.

* Rename the ws_name_XX() functions to normalize_name_map()
  and normalize_name_unmap().  Chaneg interface to return
  NTSTATUS rather than char *.

* Add associated cache validation functions.