Added include/osg/EarthSky and src/osg/EarthSky to cvs.

Also move osg across to using radians for angular paramters by default.
By defining USE_DEGREES_INTERNALLY you can get the OSG to revert to
the old style degrees. This later feature is deprecated and only meant
for helping comptability in the interim.

src/osg/EarthSky.cpp

@@ -0,0 +1,20 @@
+#include "osg/EarthSky"
+
+#include <algorithm>
+
+using namespace osg;
+
+/**
+ * EarthSky constructor.
+ */
+EarthSky::EarthSky()
+{
+    StateSet* stateset = new StateSet;
+    stateset->setRenderBinDetails(-1,"RenderBin");
+    setStateSet(stateset);
+    
+    _requiresClear = true;
+    _clearColor.set(0.0f,0.0f,0.0f,1.0f);  
+
+}
+