XML_ExpatVersionInfo(): New function; returns library version as a

XML_ExpatVersionInfo():  New function; returns library version as a
        structure that can be examined at runtime.

XML_ExpatVersion():  Construct the return value from the new version
        information constants.

XML_MAJOR_VERSION, XML_MINOR_VERSION,
XML_MICRO_VERSION:  New constants; these specify the version of the
        library in a form that can be queried by client applications
        at compile time.  This is useful in determining if functions
        should be considered available (like those above).