Longer term solution for extension name dictionaries

> I don't think it would, unfortunately, because AFAICT the extension name without any suffix is defined as an attribute by the build system, in `gen/specattribs.adoc`, the attribute just doesn't have any value so it doesn't generate any text in the spec. Maybe we could simply update the Makefile to generate attributes with some text instead, say "OOPS!", and that way at least the incorrect attribute usage wouldn't be silent?

Would it be helpful to just define the attribute's value as its name, or an xref to the extension anchor in the appendix? Trivial to do.

_Originally posted by @oddhack in https://github.com/KhronosGroup/OpenCL-Docs/issues/1131#issuecomment-2033396092_

Start by reading gen/specattribs.adoc and the Makefile generation rules for extension-name attributes. Compare the proposed attribute-value and diagnostic approaches, then confirm the intended behavior for the extension anchor in the appendix; done means the chosen handling is implemented and missing or incorrect attribute usage is no longer silent.

Written by the indexing model from the issue text.