rtnl_link: decode IFLA_AF_SPEC

rtnl_link: decode IFLA_AF_SPEC

* xlat/in6_addr_gen_mode.in: New file.
* xlat/inet6_devconf_indices.in: Likewise.
* xlat/inet6_if_flags.in: Likewise.
* xlat/inet_devconf_indices.in: Likewise.
* xlat/rtnl_ifla_af_spec_inet6_attrs.in: Likewise.
* xlat/rtnl_ifla_af_spec_inet_attrs.in: Likewise.
* xlat/snmp_icmp6_stats.in: Likewise.
* xlat/snmp_ip_stats.in: Likewise.
* rtnl_link.c: Include netinet/in.h, xlat/in6_addr_gen_mode.h,
xlat/inet_devconf_indices.h, xlat/inet6_devconf_indices.h,
xlat/inet6_if_flags.h, xlat/rtnl_ifla_af_spec_inet_attrs.h,
xlat/rtnl_ifla_af_spec_inet6_attrs.h, xlat/snmp_icmp6_stats.h,
and xlat/snmp_ip_stats.h.
(decode_ifla_inet_conf, decode_ifla_inet6_flags,
decode_ifla_inet6_conf, decode_ifla_inet6_stats,
decode_ifla_inet6_cacheinfo, decode_ifla_inet6_icmp6_stats,
decode_ifla_inet6_token, decode_ifla_inet6_agm, decode_ifla_af,
decode_ifla_af_spec): New functions.
(ifla_inet_nla_decoders, ifla_inet6_nla_decoders,
nla_decoder_table_desc): New static constant variables.
(ifinfomsg_nla_decoders) <[IFLA_AF_SPEC]>: Change value from NULL to
decode_ifla_af_spec.