Make sure that we're handling nans/infs correctly, in particular only
generating quiet nans when given a quiet nan. This catches the previous
qNaN fix.
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16233>
