[idn] summary of Punycode changes

["Adam M. Costello" <idn.amc+0@nicemice.net.RemoveThisWord>]

The changes from Punycode draft 01 to 02 are all editorial, not
technical.  Almost all were motivated by Erik Nordmark's comments, shown
below.

> The introduction of "bootstring" in the abstract is a bit odd - almost
> made me look for bootstring in the references section.

Fixed.

> Section 4 talks about mixed-case annotations but it hasn't been
> mentioned earlier in the document

It was mentioned at the end of section 1.1, but not described at all.
Now it is briefly described there.

> Section 6.2 says at the end what the decoder need not re-encode its
> output.  Why would it ever need that?

That is now explained.

> Section 6.3 talks about overflow - but is the information in that
> paragraph common to the decoder and encoder? (The text lives only in
> the encoder section.)

Yes.  That information has been relocated to section 6.4 "Overflow
handling".

> Section 7.1 talks about "the IDNA signature prefix" but the IDNA
> spec uses the term "ACE prefix".

Fixed.

> Split normative vs. non-normative references.

All references are non-normative, and the section title now reflects
that.

Additional changes:  A reference to ASCII has been added (RFC 20).  The
description of example S has been fixed to remove an erroneous claim
that it breaks the rules of Nameprep.

AMC