Poll: version minimum check
Wondering if anybody would object to the following changes to minimum dependencies -- only for master branch going forward and the NEXT major release of OSL (obviously not dropping support from release branches).
* LLVM: Current minimum we support is 7.0. LLVM 12 is current, release of LLVM 13 is imminent. It seems the burden of having to support, test, and CI SEVEN versions (7.0 - 13, inclusive) is an unnecessary burden. What's a reasonable floor going forward? Supporting five LLVM releases (the current and four prior), which seems very generous, would indicate a minimum of LLVM 9, once 13 is released.
* OptiX: For those of you using the Cuda/OptiX GPU back end, do you still need support for OptiX 6? Or can we safely be OptiX 7+ only moving forward?
* OpenImageIO: Currently, OSL master supports and tests against OIIO 2.1, 2.2, and 2.3, as well as OIIO master. Now that 2.3 is the current supported release, is there a need to actively ensure that OSL-next builds against OIIO 2.1, the release family from 2 years ago, or can we raise the floor to 2.2 (last year's release)?
* OpenEXR: I already have outstanding [PR 1406(https://github.com/AcademySoftwareFoundation/OpenShadingLanguage/pull/1406) raising the OpenEXR/Imath floor from 2.0 to 2.3, which I will merge soon if nobody objects. But is 2.3 support even necessary? Is anybody building OSL master constrained to use an OpenEXR/Imath PRIOR to 2.4?