[Bug c/28901] -Wunused-variable ignores unused const initialised variables

[mark at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=28901

--- Comment #35 from Mark Wielaard <mark at gcc dot gnu.org> ---
Note the followup patch needed for PR c/69911
https://gcc.gnu.org/viewcvs?rev=233627&root=gcc&view=rev