nfs: Remove _U_, use ccan/compiler and UNUSED

Also, add Author and License lines to _info (ccanlint complained).
Now ccanlint can build it as a module.

ccan/nfs/Makefile

 CC=gcc
-CFLAGS=-g -O0 -Wall -W -I../.. "-D_U_=__attribute__((unused))"
+CFLAGS=-g -O0 -Wall -W -I../..
 LIBS=
 
 LIBNFS_OBJ = libnfs-raw-mount.o libnfs-raw-portmap.o libnfs-raw-nfs.o libnfs-raw-nfsacl.o mount.o nfs.o nfsacl.o portmap.o pdu.o init.o socket.o libnfs.o libnfs-sync.o

ccan/nfs/_info

@@ -9,6 +9,9 @@
  * Note: various files are generated from the XDR descriptions in the rpc/
  * directory using rpcgen.
  *
+ * Author: Ronnie Sahlberg <ronniesahlberg@gmail.com>
+ * License: GPL
+ *
  * Example:
  * #include <ccan/nfs/nfs.h>
  * #include <err.h>

ccan/nfs/pdu.c

@@ -19,6 +19,7 @@
 #include <strings.h>
 #include <rpc/xdr.h>
 #include <rpc/rpc_msg.h>
+#include <ccan/compiler/compiler.h>
 #include "dlinklist.h"
 #include "nfs.h"
 #include "libnfs-raw.h"
@@ -69,7 +70,7 @@ struct rpc_pdu *rpc_allocate_pdu(struct rpc_context *rpc, int program, int versi
 	return pdu;
 }
 
-void rpc_free_pdu(struct rpc_context *rpc _U_, struct rpc_pdu *pdu)
+void rpc_free_pdu(struct rpc_context *rpc UNUSED, struct rpc_pdu *pdu)
 {
 	if (pdu->outdata.data != NULL) {
 		free(pdu->outdata.data);