[relax-ng] RELAX NG resources updated

I've updated jing, trang and dtdinst. Trang now has experimental support 
for generating W3C XML Schema.  DTDinst has a new option -i for inlining 
attribute list declarations; this makes its generated output work better as 
input for generating W3C XML Schema. Jing has a couple of minor bug fixes. 
See

  http://www.thaiopensource.com/relaxng/trang.html
  http://thaiopensource.com/dtdinst/

There are still lots of things I want to add to the trang XSD output 
module.  Feedback on what improvements are most needed is welcome.

James