Merge branch 'master' of https://github.com/openscenegraph/osg into dev

Conflicts:
	src/osgViewer/View.cpp
Merge branch 'master' of https://github.com/openscenegraph/osg into dev
From Aurelien Albert, "This submission is made against trunk version and add the loading of "glVertexAttribDivisor" extension."
Merge branch 'master' of https://github.com/openscenegraph/osg into dev
Merge branch 'dev' of https://github.com/aurelien35/osg into dev