Added desciptions to all the demos.

examples/osgvertexprogram/osgvertexprogram.cpp

@@ -345,6 +345,7 @@ int main(int argc, char *argv[])
     osg::ArgumentParser arguments(&argc,argv);
 
     // set up the usage document, in case we need to print out how to use this program.
+    arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" is the example which demonstrate support for ARB_vertex_program.");
     arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] filename ...");
     arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");