Adding portsnap to the base system

[Colin Percival]

I've been told by a committer that there hasn't been enough
discussion about the merits of adding portsnap to the base
system.

The basic summary, for anyone who didn't read yesterday's
thread, is that portsnap is a secure, easy to use, fast,
low-bandwidth, and lightweight way to keep the ports tree
up to date.  It is currently used by about 2000 systems each
week (based on my server logs; and increasing at a rate of
about 50% per month).  The feedback I've had from users has
been universally glowing, aside from the complaints that it
really should be in the base system already.

Portsnap is not a complete replacement for CVSup -- it only
handles ports, and it only handles the tree, not the repo --
but it is very good at doing the job it is designed for.

Discuss.

Unless I hear any complaints, I'm going to commit the following
patch tomorrow:
http://www.daemonology.net/tmp/portsnap-base.diff

Colin Percival