configure.ac: add -Werror to default compiler options

[Dan Kegel]

On Thu, Sep 18, 2008 at 5:17 PM, James Hawkins <truiken at gmail.com> wrote:
> I think the important thing for Dan's case is that he also used -Wall,
> which we should never turn on by default, especially not with -Werror.
>  Correct me if I've made an incorrect assumption.

Many serious projects always use both -Wall and -Werror, including Chrome.

It would be nice if Wine also became serious in this regard,
but it will take some work to get there.
- Dan