 When validating XML parser tries to resolve system entities it 
	searches in http_root directory.
	If it fails parser iterates internal list of system paths and tries to
	find required files there. The function adds new path in this list.
	List of system paths contains one direcory item by default - 
	"file://system/".
    NOTE: List of system paths is not persistent. It means that you must
	add desired path each time when server starts. An ideal place for this
	operation in "autoexec.isql" file. 