glibc 2.13.90 has obsoleted its rpc implementation in favour of
the one provided by the TI-RPC library:

> * The RPC implementation in libc is obsoleted.  Old programs keep working
>   but new programs cannot be linked with the routines in libc anymore.
>   Programs in need of RPC functionality must be linked against TI-RPC.
>   The TI-RPC implemtation is IPv6 enabled and there are other benefits.
>
>   Visible changes of this change include (obviously) the inability to
>   link
>   programs using RPC functions without referencing the TI-RPC library,
>   the
>   removal of the RPC headers from the glibc headers, and the lack of
>   symbols defined in <rpc/netdb.h> when <netdb.h> is installed.
>   Implemented by Ulrich Drepper.
(from glibc NEWS)

Thus with recent glibc, we need to try linking with -ltirpc when looking
for the XDR functions. The daemon also needs to use XDR_CFLAGS to be able
to find the XDR headers stored in /usr/include/tirpc.

When using TI-RPC, there are some warnings about redundant declarations, but
the fix probably belongs in other modules:

/usr/include/tirpc/rpc/rpcent.h:68:13: warning: redundant redeclaration of
'setrpcent' [-Wredundant-decls]
/usr/include/rpc/netdb.h:53:13: note: previous declaration of 'setrpcent'
was here

/usr/include/tirpc/rpc/rpcent.h:69:13: warning: redundant redeclaration of
'endrpcent' [-Wredundant-decls]
/usr/include/rpc/netdb.h:54:13: note: previous declaration of 'endrpcent'
was here

/usr/include/tirpc/rpc/rpc.h:84:12: warning: redundant redeclaration of
'bindresvport' [-Wredundant-decls]
/usr/include/netinet/in.h:440:12: note: previous declaration of
'bindresvport' was here