This change relates to OpenCL C 3.0 support. RFC thread: https://lists.llvm.org/pipermail/cfe-dev/2020-September/066883.html
The same interface ('-cl-ext' option) is being used to indicate that feature or extension is supported. OpenCL C 3.0 by default doesn't provide any features which are core in OpenCL C 2.0. The idea is to define feature test macros for all OpenCL versions and provide simultaneous macro presence if there exist equivalent extension.
Btw I guess we don't need the last parameter for the features since it's always 0?