[osg-users] Please test OpenSceneGraph-3.6 branch in prep for 3.6.1

[Robert Osfield]

Hi Dan et. al,

> I am currently testing the OSG_GL3_FEATURES change for defaulting version to 3.3, and still plan to have a PR in the next hour or two once my builds finish.

After merging your change I had a further think about the issue and
decided that using CMake would be better so have checked in the
commit:

    https://github.com/openscenegraph/OpenSceneGraph/commit/1aa0a80de7f0afeb044098637216a80752e4ab07

I have done a few tests and things look to be working OK, would
appreciate others to test and make sure it's working fine.

Cheers,
Robert.