What extensions need to be reported through `CL_PLATFORM_EXTENSIONS`

One sentence in the spec which I'm not entirely sure how to parse is "Each extension that is supported by all devices associated with this platform must be reported here.".

As of now in rusticl/mesa we only report extensions which don't rely on any hardware support and only those we promise to support on every possibly supported device.

However one could also read this as "extensions supported by all devices by this platform need to be listed there". "all devices" as in all the currently available and listed ones.

We are probably one of the few OpenCL implementations where distinguishing between those two interpretations might even matter and I was wondering if it makes sense to clarify this or what the actual intention here was.

Start by examining the quoted CL_PLATFORM_EXTENSIONS requirement in the relevant OpenCL specification and compare its two possible interpretations with the rusticl/mesa behavior described here. Determine which meaning is intended and clarify the specification wording so the reporting rule is unambiguous for implementations with multiple devices.

Written by the indexing model from the issue text.