Now that all the hooks are in place, this large patch imports all
of the new code for the NFSv4 client.
  nfs4proc.c   - procedure vectors
  nfs4xdr.c    - XDR
  nfs4state.c  - state bookkeeping (very minimal for now)
  nfs4renewd.c - a daemon (implemented as an rpc_task) to keep
                 state from expiring on the server

Note: The RPCSEC_GSS authentication code is not yet included here.
  For the moment we make do with AUTH_UNIX aka. AUTH_SYS.

  Neither is the code to do upcalls to userland in order to do
  uid/gid <-> name mappings. Instead, stubs have been added to
  translate everything to 'nobody:nobody' == '-2:-2'