Added DisplaySetting::s/getCompileContextHint() and use of this hint in osgViewer::Viewer/CompositeViewer.

Removed the CustomViewer in osgterrain example as the above now removes the need for it.

src/osgViewer/Viewer.cpp

@@ -935,6 +935,27 @@ void Viewer::realize()
     setStartTick(osg::Timer::instance()->getStartTick());
 
     setUpThreading();
+    
+    if (osg::DisplaySettings::instance()->getCompileContextsHint())
+    {
+        int numProcessors = OpenThreads::GetNumberOfProcessors();
+        int processNum = 0;
+
+        for(unsigned int i=0; i<= osg::GraphicsContext::getMaxContextID(); ++i)
+        {
+            osg::GraphicsContext* gc = osg::GraphicsContext::getOrCreateCompileContext(i);
+
+            if (gc)
+            {
+                gc->createGraphicsThread();
+                gc->getGraphicsThread()->setProcessorAffinity(processNum % numProcessors);
+                gc->getGraphicsThread()->startThread();
+                
+                ++processNum;
+            }
+        }
+    }
+    
 }