Protect ping(8) using Capsicum and Casper. This is protection against malicious
network packets that we parse and not against local users trying to gain root
access through ping's set-uid bit - this is handled by dropping privileges very
early in ping.

Submitted by:	Mikhail <mp@lenta.ru>
Fix installations that use kernels without CAPABILITIES support.

Approved by:	des
Add a license (1) and do some cleanup.

Approved by:	Stefan Bethke (original author, by private mail) (1)
MFC after:	1 week