[relax-ng] Jing update

[James Clark <jjc@jclark.com>]

I've released a new version of Jing:

 http://thaiopensource.com/relaxng/jing.html

There are a lot of changes in this release:

- the ID/IDREF/IDREFS checking part of DTD Compatibility is implemented

- I've almost completely rewritten the validator using an improved algorithm

- there's a documented API for Jing; in fact there are two APIs, a native
API
and JARV

I've also created a page with pointers to information about implementing
RELAX NG

  http://thaiopensource.com/relaxng/implement.html

I've also rewritten the description of derivative-based validation to
correspond to what I've implemented and to incorporate the feedback I
received on the previous version from Murata-san and Kawaguchi-san:

  http://thaiopensource.com/relaxng/derivative.html

In the old algorithm, the state of the validation was represented by a stack
of sets of patterns.  In the new algorithm, the state is represented by a
single pattern. To enable this it introduces a new kind of pattern: x/y
matches x followed by an end-tag followed by y.  The old algorithm optimized
the common case where there was only a single content model possible for an
element of a given name.  The new algorithm no longer makes this a special
case; it doesn't improve significantly on this common case, but it is much
more efficient for other cases.  In particular, it can handle quite
efficiently the case which would arise from translating W3C XML Schema,
where there are many content models possible for an element name (according
to the value of xsi:type).

There's also a new error recovery strategy (details in the above document).

James