Multiple potential exceptions: nodereplacechildnewchilddiffdocument

nodereplacechildnewchilddiffdocument.xml is a strange case.  

It calls Node.replaceChild with a old node that is not a child of the target node and attempts to replace it with a node that isn't part of this document.  So it could conceivable throw either NOT_FOUND_ERR or WRONG_DOCUMENT_ERR depending on which condition it tested first.  I don't believe there is anything in the DOM spec that would prescribe which exception code should take precedence and DOMTSML doesn't have a construct to support an ambiguous exception code.

The test is internally inconsistant since the description says
The "replaceChild(newChild,oldChild)" method raises a 
WRONG_DOCUMENT_ERR DOMException if the "newChild" was
created from a different document than the one that 
created this node.

But the test checks for NOT_FOUND_ERR.  I'm going to make the body consistent with the description.