[Bug c/79696] missing -Wunused-result on calls to malloc() and calloc()

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79696

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
-Wunused-result warns on the attribute warn_unused_result usage.  If these
functions are not marked that way in glibc, it is maybe a glibc bug.
I don't think we should mark these as warn_unused_result really.