[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 #6 from Sam James <sjames at gcc dot gnu.org> ---
(In reply to Sam James from comment #5)

I brought it up at
https://social.treehouse.systems/@thesamesam/110148110341108345 too where
[[unsequenced]] and [[reproducible]]  were mentioned.