Use callout(9) instead of timeout(9).

Reviewed by:	emax
PTRACE HARDENING: slight update.
Merge branch 'hardened/current/ptrace' of https://github.com/HardenedBSD/hardenedBSD into hardened/current/ptrace
Revert changes in r269180.  It could cause -c N option to enter an
infinite loop if no reply packet is received.

PR:	151023
Fix a problem that reply packets are not received when -i T option is set
and (T < RTT).

- Use select(2) for timeout instead of interval timer. Remove poll(2) support.
- Use sigaction(2) instead of signal(3).
- Exit in SIGINT handler when two signals are received and doing reverse DNS
  lookup as ping(8) does.
- Remove redundant variables used for getaddrinfo(3).

PR:	151023
Add unit tests for mkimg(1):
Merge remote-tracking branch 'freebsd/master' into hardened/current/master
Merge remote-tracking branch 'freebsd/master' into hardened/current/hardening
Merge remote-tracking branch 'freebsd/master' into hardened/current/segvguard
Merge remote-tracking branch 'freebsd/master' into hardened/current/ptrace
Merge remote-tracking branch 'freebsd/master' into hardened/current/log
Merge remote-tracking branch 'freebsd/master' into hardened/current/userlandenhanced
Merge branch 'hardened/current/master' into hardened/current/unstable
Merge branch 'hardened/current/hardening' into hardened/current/unstable
Merge branch 'hardened/current/segvguard' into hardened/current/unstable
Merge branch 'hardened/current/ptrace' into hardened/current/unstable
Merge branch 'hardened/current/log' into hardened/current/unstable
Merge branch 'hardened/current/userlandenhanced' into hardened/current/unstable