Fixed VS2015 compiler warnings
Fixed VS2015 compiler warnings

tomasthoresen/osg,scrawl/osg,scrawl/osg,openscenegraph/osg,marchelbling/osg,jtorresfabra/osg,artoolkit/osg,marchelbling/osg,tomasthoresen/osg,artoolkit/osg,marchelbling/osg,scrawl/osg,tomasthoresen/osg,marchelbling/osg,scrawl/osg,artoolkit/osg,openscenegraph/osg,artoolkit/osg,jtorresfabra/osg,openscenegraph/osg,openscenegraph/osg,tomasthoresen/osg,jtorresfabra/osg,jtorresfabra/osg