Adds support for the PI-based architecture use
declaration syntax defined by Amendment 1 to ISO/IEC
10744:1997 (HyTime). This makes it possible to specify
architectural support attributes when using
architectures with XML, and is generally simpler than
the original syntax. See
http://www.ornl.gov/sgml/wg8/document/1985.htm for details.
This patch also makes it possible to, and provides an
example of how to, use the exisiting attribute
specification parsing machinery to process attribute
specifications within processing instructions.