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/TrackballManipulator.cpp

@@ -54,7 +54,7 @@ void TrackballManipulator::home(double /*currentTime*/)
 
 void TrackballManipulator::home(const GUIEventAdapter& ea ,GUIActionAdapter& us)
 {
-    home(ea.time());
+    home(ea.getTime());
     us.requestRedraw();
 }
 
@@ -167,7 +167,7 @@ bool TrackballManipulator::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);
 }