XML Backend to compile with disabled XML

Classes
class	CLAM::NullDomDocumentHandler
	Dummy implementation of a DomDocumentHandler when XML is disabled. More...
class	CLAM::NullDomReadingContext
	Dummy implementation of a DomDocumentReadingContext when XML is disabled. More...
class	CLAM::NullDomWritingContext
	Dummy implementation of a DomDocumentWritingContext when XML is disabled. More...