xpath improvement suggestion

Hi all,

Well I had  to burn some midnight oil trying to figure out why a 
construct like
SELECT xpath('name()','<a/>');
doesn't give the expected result. Kept getting an empty array:
   xpath
-------------
{}
instead of the expected "{a}"
BugID 4294 and the TODO item "better handling of XPath data types" 
pointed in the right direction.
whithin src/backend/utils/adt/xml.c in the function xpath the result of 
the call to xmlXPathCompiledEval is not handled optimally. In fact, the 
result is assumed to be a nodeset without consulting the ->type member 
of the result. I've made some minor changes to xml.c to handle some 
non-nodeset results of xmlXPathCompiledEval.
Essentially, the revised code makes an array of all the nodes in the 
xpathobj result in case this is a nodeset, or an array with a single 
element in case the reult is a number/string/boolean. The problem cases 
mentioned in 
http://archives.postgresql.org/pgsql-hackers/2008-06/msg00616.php now 
work as expected.
Revision of the code involves:
- A switch statement to handle the result type of xmlXPathCompiledEval.
- an additional function xmlpathobjtoxmltype.

diff of the revisioned code with respect to original is in attached file.

kind regards, Arie Bikker