Implement IPPROTO_IP control messages decoding

Implement IPPROTO_IP control messages decoding

* net.c: Include "xlat/ip_cmsg_types.h".
(print_cmsg_ip_pktinfo, print_cmsg_ip_ttl, print_cmsg_ip_tos,
print_cmsg_ip_opts, print_cmsg_ip_recverr, print_cmsg_ip_checksum,
print_cmsg_ip_origdstaddr): New functions.
(print_cmsg_type_data): Add generic SOL_IP level decoding.
Use these functions for decoding of IP_PKTINFO, IP_TTL, IP_TOS,
IP_RECVOPTS, IP_RETOPTS, IP_RECVERR, IP_ORIGDSTADDR, IP_CHECKSUM,
and SCM_SECURITY type messages.
* xlat/ip_cmsg_types.in: New file.
* xlat/sockipoptions.in: Move IP_RETOPTS before IP_RECVRETOPTS.
* tests/inet-cmsg.c: New file.
* tests/inet-cmsg.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add inet-cmsg.
(TESTS): Add inet-cmsg.test.
* tests/.gitignore: Add inet-cmsg.

Suggested-by: Orion Poplawski <orion@cora.nwra.com>