Unified the setup of version numbers so that they all are based on the version

number setup in the include/osg/Version header file.

src/osgViewer/Version.cpp

@@ -1,8 +1,11 @@
 #include <osgViewer/Version>
+#include <osg/Version>
+
+extern "C" {
 
 const char* osgViewerGetVersion()
 {
-    return "1.9";
+    return osgGetVersion();
 }
 
 
@@ -10,3 +13,5 @@ const char* osgViewerGetLibraryName()
 {
     return "OpenSceneGraph Viewer Library";
 }
+
+}