NFS: Add a dns resolver for use with NFSv4 referrals and migration

The NFSv4 and NFSv4.1 protocols both allow for the redirection of a client
from one server to another in order to support filesystem migration and
replication. For full protocol support, we need to add the ability to
convert a DNS host name into an IP address that we can feed to the RPC
client.

We'll reuse the sunrpc cache, now that it has been converted to work with
rpc_pipefs.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
index 8451598..da7fda6 100644
--- a/fs/nfs/Makefile
+++ b/fs/nfs/Makefile
@@ -6,7 +6,8 @@
 
 nfs-y 			:= client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \
 			   direct.o pagelist.o proc.o read.o symlink.o unlink.o \
-			   write.o namespace.o mount_clnt.o
+			   write.o namespace.o mount_clnt.o \
+			   dns_resolve.o cache_lib.o
 nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
 nfs-$(CONFIG_NFS_V3)	+= nfs3proc.o nfs3xdr.o
 nfs-$(CONFIG_NFS_V3_ACL)	+= nfs3acl.o