Added include<osg/AlphaFunc> for OSX build
Added include<osg/AlphaFunc> for OSX build


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