[Bug c/88430] -Wmissing-attributes warnings when including libquadmath headers

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88430

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
The change occurred between r265975 (no warning) and r266035 (warnings).