This simplifies completeness comparisons against OpenCLBuiltins.td and
also makes the header no longer "claim" the identifiers "success",
"failure", "desired", "value" (such that you can compile with -Dvalue=...
when including the header for example, which currently breaks parsing
of the header).
I made this patch to be able to do some completeness comparisons locally
for D119420, and thought it might be worth committing anyway.
This is a big patch and it only touches the OpenCL 2 atomics for now. I
wonder if we should remove argument names from the other builtins too?
I think it would help unifying the header and tablegen approaches: if we
gradually move the header into some canonical form, we might be able
to eventually replace it with a tablegen-ed header, while being able to
easily confirm equivalence.