[relax-ng] RELAX NG resources updated

I've updated Jing and other RELAX NG resources at

   http://www.thaiopensource.com/relaxng/

This is a relatively minor update.  Changes are as follows.

- I've implemented the errata for ID/IDREF checking and choice name classes.

- I've implemented a suggestion by Rick Jellife to support "feasible
validation".  If you use a -f option with Jing, it will first transform the
schema by wrapping each element, attribute, data and list element in an
optional element and will then validate against this transformed schema.
The net result is to check whether the document could be made valid by
inserting additional elements and attributes. This may be useful for
documents that are still under construction.

- In the compact syntax, the xsd prefix is predeclared.

- The XHTML schema provides a solution to the problem of exclusions.  For
more on this, see the last bulleted item in:

http://www.thaiopensource.com/relaxng/xhtml/

- A couple of compact syntax parsing bugs are fixed.

James