Fix typos and spelling.

examples/osgcluster/osgcluster.cpp

@@ -509,7 +509,7 @@ int main( int argc, char **argv )
     // any option left unread are converted into errors to write out later.
     arguments.reportRemainingOptionsAsUnrecognized();
 
-    // report any errors if they have occurred when parsing the program aguments.
+    // report any errors if they have occurred when parsing the program arguments.
     if (arguments.errors())
     {
         arguments.writeErrorMessages(std::cout);