* include/rpc/auth.h: Mark xdr_des_block_internal and
xdr_opaque_auth_internal as hidden.
* sysdeps/unix/sysv/linux/getdents.c: Mark __have_no_getdents64 as
hidden.
* include/rpc/xdr.h: Make all _internal functions as hidden.
* sunrpc/pmap_rmt.c: Declare xdr_rmtcall_args_internal as hidden.