- Add sysdeps to test ut_addr_v6 in utmp and utmpx
- We already have the remote IP as a string, we just add a
decoding step in logsys_utmp(x) to fill the addr field.
- We assume arpa/inet.h and AF_INET6 exist on the system.
If the build fails on (ancient) systems, sysdeps will need to
be added to test for them.

Signed-off-by: Laurent Bercot <ska@appnovation.com>