P/santoch/cr/nchk2708

@apond 
per the spec(s), the xml documents must be xml 1.0, not 1.1, for 2.0.1 and later.
moving the check into the base class allows it to be called for both 2.0 and 3.0 documents.
also, the wrapper logic was wrong.  It would only skip calling it if the version check reported back that it WAS an invalid version.  Otherwise, it called the check on every element in the document, a huge perf loss.