[Bug c/87435] "Duplicate const" warning NOT emitted from typedef in -std=c90

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87435

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>(non pedantic, non GNU)

Yes you need to use -pedantic-errors to get fully complaint compiler errors.  I
think this was always designed that way.