Move family-specific NETLINK_SOCK_DIAG parsers to separate files

Move family-specific NETLINK_SOCK_DIAG parsers to separate files

Split netlink_sock_diag.c that grew too big.

* defs.h (tcp_states, tcp_state_flags): New xlat prototypes.
* netlink_sock_diag.h: New file.
* netlink_inet_diag.c: Likewise.
* netlink_netlink_diag.c: Likewise.
* netlink_packet_diag.c: Likewise.
* netlink_smc_diag.c: Likewise.
* netlink_unix_diag.c: Likewise.
* Makefile.am (strace_SOURCES): Add them.
* netlink_sock_diag.c: Move family-specific parsers and associated
header includes to separate files.
* nlattr.h (DECL_NLA(meminfo)): New prototype.
* nlattr.c: Include <linux/sock_diag.h>.
(print_meminfo, decode_nla_meminfo): New functions from
netlink_sock_diag.c.