[developers] SBCL port: XML

[Ben Waldron]

The current LKB relies on the :pxml module ("A Lisp Based XML Parser": 
http://www.franz.com/support/documentation/8.0/doc/pxml.htm) which is 
distributed with Allegro lisp. This module is Allegro-specific. In 
particular, it /doesn't/ compile with SBCL lisp.

An alternative module is S-XML ("a simple XML parser implemented in 
Common Lisp": http://common-lisp.net/project/s-xml/). The interface to 
S-XML is sufficently similar to :pxml that it appears possible to simply 
swap these two modules whilst leaving the LKB source code unchanged; and 
it has the great advantage of running under /any/ Common Lisp (in 
particular SBCL). (Namespace support appears subtly different, but I 
don't think this is an issue.)

I've tested that S-XML can be used to replace the existing 
Allegro-specific XML module in the LKB. I would like to make such a swap 
official. Any objections?

Thanks,
- Ben