Converted osgGA::GUIEventAdapter into a concrete class capable of respresenting

keyboard and mouse events.

Added osgGA::EventQueue class to support a thread safe event queue and adaption
of keyboard and mouse events.

Removed osgProducer::EventAdapter as GUIEventAdapter replaces it.

Adapted osgProducer and examples to work with the new changes to osgGA.

src/osgGA/NodeTrackerManipulator.cpp

@@ -288,7 +288,7 @@ bool NodeTrackerManipulator::isMouseMoving()
     float dx = _ga_t0->getXnormalized()-_ga_t1->getXnormalized();
     float dy = _ga_t0->getYnormalized()-_ga_t1->getYnormalized();
     float len = sqrtf(dx*dx+dy*dy);
-    float dt = _ga_t0->time()-_ga_t1->time();
+    float dt = _ga_t0->getTime()-_ga_t1->getTime();
 
     return (len>dt*velocity);
 }