#22 Add Simple API for XML (SAX) support.

[Derrick Oswald]

Use the interfaces found at project SAX
(http://sourceforge.net/projects/sax/) to implement a
(SAX compliant?) 'XMLReader' object.

[Derrick Oswald]

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Preliminary implementation based on DOM parser complete.
Requires namespace support in DocTypeTag and for attributes
of composite tags.