Merge branch 'ss-rpcinfo' into next

Andrea Claudi  says:

====================

ss uses rpcinfo to get info about rpc service sockets. However, rpcinfo
is not part of iproute2 and it's an implicit dependency for ss.

This series uses libtirpc[1] API to implement the same feature of
rpcinfo for ss. This makes it possible to get info about rpc sockets,
provided ss is compiled with libtirpc support.

As a nice byproduct, this makes ss provide info about some ipv6 rpc
sockets that are not displayed using 'rpcinfo -p'.

- patch 1 adds a configure function to check for libtirpc;
- patch 2 actually rework ss to use libtirpc.

[1] https://git.linux-nfs.org/?p=steved/libtirpc.git

====================

Signed-off-by: David Ahern <dsahern@kernel.org>