Embree v2.15.0

• Added rtcCommitJoin mode that allows thread to join a build operation. When using the internal tasking system this allows Embree to solely use the threads that called rtcCommitJoin to build the scene, while previously also normal worker threads participated in the build. You should no longer use rtcCommit to join a build.
• Added rtcDeviceSetErrorFunction2 API call, which sets an error callback function which additionally gets passed a user provided pointer (rtcDeviceSetErrorFunction is now deprecated).
• Added rtcDeviceSetMemoryMonitorFunction2 API call, which sets a memory monitor callback function which additionally get passed a user provided pointer. (rtcDeviceSetMemoryMonitorFunction is now deprecated).
• Build performance for hair geometry improved by up to 2x.
• Standard BVH build performance increased by 5%.
• Added API extension to use internal Morton-code based builder, the standard binned-SAH builder, and the spatial split-based SAH builder.
• Added support for BSpline hair and curves. Embree uses either the Bezier or BSpline basis internally, and converts other curves, which requiring more memory during rendering. For reduced memory consumption set the EMBREE_NATIVE_SPLINE_BASIS to the basis your application uses (which is set to BEZIER by default).
• Setting the number of threads through tbb::taskscheduler_init object on the application side is now working properly.
• Windows and Linux releases are build using AVX512 support.
• Implemented hybrid traversal for hair and line segments for improved ray packet performance.
• AVX512 code compiles with Clang 4.0.0
• Fixed crash when ray packets were disabled in CMake.