message: add ISPC/Embree version and pre-built binraries known issue items
diff: @@ -66,6 +66,11 @@ Version History
  - The old variant of `ospNewData` was temporarily retained in
  `ospray_util.h` for C++ applications and will be removed for the
  official v2.0 release
  + - ISPC v1.11.0 and Embree v3.6.0 are both incompatible with OSPRay
  + and should be avoided (OSPRay should catch this during CMake
  + configure)
  + - This is a source-only release, binaries will be made available
  + for the official v2.0.0 release
  ### Changes in v1.8.5:
  