First version of internals tour committed

[Eric S. Raymond]

There is a new document, devel/tour.txt, describing the internals of NTP
at a level above in-code comments.  This is a serious effort to shine light
into murky corners and improve the maintainability of the code.

Please read it, and add to it where you can.  When you find a "gotcha"
that is not easily described in a comment attached to a single oiece
of code, the tour document is where to put it.

I started this as part of preparing for the hard part of TESTFRAME.

I am very close to having capture mode done now.  The only remaining
problem is that the recvbuf structure passed to the protocol engine
for each completed packet is a fscking mess.  It has two different
source address fields!  One of them embedded in an untagged union.  I
need to unscramble all that before I can write the last capture method
and start on replay.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>