osg: Update to 3.6.5

OpenSceneGraph 3.6 release
Updates include:

  * OpenThreads::Affinity introduced to enable setting of processor affinity on viewer and database threads
  * osgText rewritten to improve visual quality, add signed distance field support and full GLES2/3 and GL3/4 support
  * Added VertexArrayObject support, enable full OpenGL Core Profile support under OSX.
  * Added OpenCASCADE plugin
  * Added STEP (.stp) plugin
  * Improvements to FBX and COLLADA loaders
  * Improvements to gles plugin to provide better Sketchfab support
  * Added osgemscripten example
  * Improvements to osgAnimation
  * NodeVisitor ValueMap for storing values that can be stored and accessed across frames, such as update, event and cull traversals
  * ShapeDrawable rewritten as an osg::Geometry to improve performance and flexibility
  * Added osg::MultiDrawArrays support
  * Added osgdeferred example that illustrates how to implement deferred rendering
  * Added MultiDrawIndirect support
  * Moved glDispatchCompute control out of osg::Program into a dedicated osg::DispatchCompute class to improve control of compute shaders
  * KdTree support added for PolytopeIntersector, and ability to work with points, lines and polygons
  * osgQt has been moved out to it's own dedicated osgQt github repository
  * CMake build support for iOS bitcode builds
  * CoverityScan testing introduced, fixes bring defect density to 0.0 per 1,0000 lines of code!
  * Support for Codedoc automated documentation
  * Support for Travis automated build system

(nia)