[Bug libstdc++/94080] -mabi=ieeelongdouble and -mfloat128 cause libstc++ header breakage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94080

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Due to a server move, bugzilla seems to have lost the original comments on this
bug. They are archived at
https://gcc.gnu.org/ml/gcc-bugs/2020-03/msg01310.html
and
https://gcc.gnu.org/ml/gcc-bugs/2020-03/msg01320.html