Added the default usage of ShaderGenVisitor to help with GLES2 testing.
Added the default usage of ShaderGenVisitor to help with GLES2 testing.


omega-hub/osg,koshman86/osg,omega-hub/osg,koshman86/osg,koshman86/osg,XiaoCC/osg,ghub/osg,koshman86/osg,ntoand/osg,XiaoCC/osg,omega-hub/osg,ghub/osg,ntoand/osg,stmh/osg,omega-hub/osg,artoolkit/osg,stmh/osg,ghub/osg,stmh/osg,XiaoCC/osg,stmh/osg,artoolkit/osg,artoolkit/osg,XiaoCC/osg,artoolkit/osg,ntoand/osg,XiaoCC/osg,ntoand/osg,ghub/osg,stmh/osg