[Bug middle-end/79720] [6/7 Regression] complex division different at compile time / runtime

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79720

--- Comment #6 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> but gcc 6 and 7 fail.

So does 4.8, 4.9, and 5.

IMO this PR should be closed as invalid: the assumption that the roundoff
errors don't depend on the optimization level is wrong.