[clang] [Clang] Add support for missing OpenCL extensions (PR #129777)

[Sven van Haastregt via cfe-commits]

https://github.com/svenvh requested changes to this pull request.

What is the motivation for this change?  We are trying to move away from adding extensions to this file for extensions that only add builtin functions, see e.g. https://reviews.llvm.org/D92231 .  What functionality are you gaining by adding them here?

https://github.com/llvm/llvm-project/pull/129777