nfs41: client xdr definitions

Define stubs for sequence args and res data structures and embed
them in all other nfs4 and nfs41 xdr types.  They are needed for
sending any op in a nfs41 compound rpc.

Signed-off-by: Andy Adamson<andros@netapp.com>
[moved new args/res definitions away, to where they're first used]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>