GLWidget : Work around warning messages on OSX/Qt5
GLWidget : Work around warning messages on OSX/Qt5

These appeared to be harmless, but were being spewed into the terminal at quite a rate.

hradec/gaffer,hradec/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,boberfly/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,boberfly/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,lucienfostier/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,hradec/gaffer,appleseedhq/gaffer,GafferHQ/gaffer,hradec/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,ivanimanishi/gaffer,boberfly/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,boberfly/gaffer,ImageEngine/gaffer,hradec/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,ivanimanishi/gaffer