The function table symbol declared in the headers was renamed starting in OptiX 8.1, from `g_optixFunctionTable` to `g_optixFunctionTable_<ABI version>`. This adds support for that by using the new macro for the name when available (after OptiX 8.1) and falling back to the old name when it is not (before OptiX 8.1). Pull Request: https://projects.blender.org/blender/blender/pulls/130451