Re: XercesDocumentBridge and XML_DECL_NODE

[Joseph_Kesselman]

XML_DECL_NODE is not part of the DOM standard.  Don't expect tools based on
the standard to handle it successfully.

(I suppose we could skip over nonstandard node types, but I think the
assert really is desirable -- at least as the default behavior -- to warn
you that the results may not be what you expected.)