NSXMLNode copyWithZone: is broken for Processing Instructions

[Doug Simons]

Fred,

One of your recent changes to NSXMLNode's copyWithZone: now causes the content 
of some nodes (processing instructions, at least) to be lost in the copy. The 
call to setObjectValue: is the culprit, as it in turn calls setStringValue: 
(with a nil value, at least in the case I traced through) which erases the 
content of the libxml node.

I'm not sure what the motive was for your recent change, but take a look and 
see if you can resolve this problem.

Thanks,

Doug