[Bug c/116130] Implement C23 N2956 paper - [[unsequenced]] and [[reproducible]] function type arguments

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116130

--- Comment #5 from Sam James <sjames at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #4)
> BTW, the rule about composite types sounds fairly dangerous in the ?:
> operator case.
> For redeclarations it is the right thing, but for ?: yielding the union of
> the standard attributes will cause problems say on:

Clang had this problem before with noreturn in
https://github.com/llvm/llvm-project/issues/59792#issuecomment-1369314436.

https://reviews.llvm.org/D140868#4024060 has discussion of the problematic
phrasing.