apinger: add apinger package

apinger: add apinger package

Alarm Pinger (apinger) is a little tool which monitors various IP devices by
simple ICMP echo requests. There are various other tools, that can do this,
but most of them are shell or perl scripts, spawning many processes, thus much
CPU-expensive, especially when one wants continuous monitoring and fast
response on target failure.

Signed-off-by: Alex Samorukov <redacted>