remove a warning when compiling with GL3 core profile and macOS
remove a warning when compiling with GL3 core profile and macOS

jtorresfabra/osg,scrawl/osg,jtorresfabra/osg,scrawl/osg,jtorresfabra/osg,marchelbling/osg,openscenegraph/osg,openscenegraph/osg,marchelbling/osg,marchelbling/osg,marchelbling/osg,openscenegraph/osg,jtorresfabra/osg,scrawl/osg,openscenegraph/osg,scrawl/osg