Fixed a bug in the drive manipulator which was due to it using the local

coords of the intersection point with the scene rather than the world
coord value for that point.  The code now uses
osgUtil::Hit::getWorldIntersectionPoint() method for getting the world coords.

Added support for getWorldIntersectionPoint to Viewer.cpp.

Put and #ifdef around the setting of the default display list visitor so
it nolonger sets in under IRIX. This is a world around to the IR graphics
imbending lighting info into display lists, if the display lists are
created before state is set up it produces lighting artifacts such as
flickering.  Remove the the default display list init visitor removes
these problems, display lists are then built on the fly and drawables
a drawn for the first time.

src/osgUtil/SceneView.cpp

@@ -61,9 +61,15 @@ void SceneView::setDefaults()
     _renderStage = new RenderStage;
 
 
+#ifndef __sgi
+    // sgi's IR graphics has a problem with lighting and display lists, as it seems to store 
+    // lighting state with the display list, and the display list visitor doesn't currently apply
+    // state before creating display lists. So will disable the init visitor default, this won't
+    // affect functionality since the display lists will be created as and when needed.
     DisplayListVisitor* dlv = new DisplayListVisitor();
     dlv->setState(_state.get());
     _initVisitor = dlv;
+#endif
 
     _appVisitor = new AppVisitor;