rtnl_tc: decode tcmsg netlink attributes

rtnl_tc: decode tcmsg netlink attributes

* configure.ac (AC_CHECK_TYPES): Check for gnet_stats_basic,
gnet_stats_queue, gnet_stats_rate_est,
and gnet_stats_rate_est64 structures in <linux/gen_stats.h>.
And check for struct tc_sizespec in <linux/pkt_sched.h>.
* nlattr.h (tc_stats): New prototype.
* rtnl_tc.c: Include <linux/gen_stats.h>, <linux/pkt_sched.h>,
"xlat/rtnl_tca_stab_attrs.h" and "xlat/rtnl_tca_stats_attrs.h".
(decode_tc_stats, decode_tc_estimator, decode_gnet_stats_basic,
decode_gnet_stats_rate_est, decode_gnet_stats_queue,
decode_gnet_stats_rate_est64, decode_nla_tc_stats,
decode_tc_sizespec, print_stab_data, decode_tca_stab_data,
decode_tca_stab): New functions.
(tca_stats_nla_decoders, tca_stab_nla_decoders,
tcmsg_nla_decoders): New arrays.
(decode_tcmsg): Use tcmsg_nla_decoders.
* xlat/rtnl_tca_stab_attrs.in: New file.
* xlat/rtnl_tca_stats_attrs.in: Likewise.