OSPRay v2.11.0

• Support single ISPC target on Windows
• OSPRay's superbuild can now be provided a CMake toolchain file for
  cross-compilation
• Add support for double pumped NEON instruction on ARM64
• Reduce the memory overhead of the mpiOffload device and resolve
  memory and MPI_Comm handle leaks
• Support for volume rendering (and thus the dependency to Open VKL)
  can now be compile-time controlled via CMake variable
  OSPRAY_ENABLE_VOLUMES
• OSPRay's MPI modules have been split up and renamed, the mpiOffload
  device is now in the mpi_offload module, while the mpiDistributed
  device is now in the mpi_distributed_cpu module
• Add native support for spheres via Embree, which requires the
  positions and radius of the spheres to be interleaved in memory; if
  this is not the case, OSPRay will internally create a copy of the
  data
• Fix dynamicScene flag on World and Group to influence BVH quality
  again: default is now "high", which should improve rendering
  performance, depending on the scene; and "low" when dynamicScene
  is enabled (improving BVH build performance)
• Fix a crash in pathtracer when there are no lights
• Fix a data corruption bug when setting string parameters for objects
  in the mpiOffload device
• Various documentation fixes
• OSPRay now has a new dependency, which is ISPC Run Time (ISPCRT) in
  minimum 1.19.0 version
• Adapt to Embree v4.0.0 API changes, which is thus the new minimum
  version; additionally, the new minimum version for Open VKL is
  v1.3.2 and for ISPC v1.19.0
• Removed support of MSVC14.0 (Visual Studio 2015) and the second
  generation Intel Xeon Phi processor (codename Knights Landing)