SUNRPC: introduce rpcbind: replacement for in-kernel portmapper

Introduce a replacement for the in-kernel portmapper client that supports
all 3 versions of the rpcbind protocol.  This code is not used yet.

Original code by Groupe Bull updated for the latest kernel, with multiple
bug fixes.

Note that rpcb_clnt.c does not yet support registering via versions 3 and
4 of the rpcbind protocol.  That is planned for a later patch.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 745afc1..fa89ce6 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -152,6 +152,7 @@
 	unsigned long		state;		/* transport state */
 	unsigned char		shutdown   : 1,	/* being shut down */
 				resvport   : 1; /* use a reserved port */
+	unsigned int		bind_index;	/* bind function index */
 
 	/*
 	 * Connection of transports