Added code into osg::LightSource so it correctly computes its bounding

sphere, taking into account any subgraph below, and the light itself
if it is not a infinite light.

src/osg/LightSource.cpp

@@ -42,9 +42,21 @@ void LightSource::setLocalStateSetModes(const StateAttribute::GLModeValue value)
 
 const bool LightSource::computeBound() const
 {
-    // note, don't do anything right now as the light itself is not
-    // visualised, just having an effect on the lighting of geodes.
-    _bsphere.init();
+    Group::computeBound();
+    
+    if (_light.valid())
+    {
+        const Light* light = dynamic_cast<const Light*>(_light.get());
+        if (light)
+        {
+            const Vec4& pos = light->getPosition();
+            if (pos[3]!=0.0f)
+            {
+                float div = 1.0f/pos[3];
+                _bsphere.expandBy(Vec3(pos[0]*div,pos[1]*div,pos[2]*div));
+            }
+        }
+    }
 
     _bsphere_computed = true;