[RFA 6/6] Add -Wunused-but-set-* to build

[Trevor Saunders]

On Mon, Jun 06, 2016 at 03:33:32PM -0600, Tom Tromey wrote:
> This adds -Wunused-but-set-variable and -Wunused-but-set-parameter to
> configure.

 great, I started on that a little while ago but didn't get to pushing
 these bits upstream.

> +++ b/gdb/warning.m4
> @@ -39,7 +39,7 @@ fi
>  build_warnings="-Wall -Wpointer-arith \
>  -Wno-unused -Wunused-value -Wunused-function \
>  -Wno-switch -Wno-char-subscripts \
> --Wempty-body"
> +-Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable"

isn't everything in -Wunused enabled now? can we just delete -Wno-unused
and use -Wall to get us -Wunused?

Trev