[BusyBox] feature patch: ping

[Bob Keyes]

I know this isn't the time to submit new features, but I thought I'd just
pass it along for anyone interested, and then re-submit it when the
development branch is started.

p2ping is a protocol for discovering file services on a LAN by pinging the
broadcast address with a modified packet, and listening for specific
responses. It was designed for network bootstrap in ad-hoc wireless mesh
networks, but may find other uses. See http://xa.net/p2ping for more
details, and patches.

Bob Keyes