configure.ac: add -Werror to default compiler options

[Dan Kegel]

On Thu, Sep 18, 2008 at 5:10 PM, Juan Lang <juan.lang at gmail.com> wrote:
>> Are you sure about that?  When I configure with -Wall -Werror,
>> I can't even configure properly; one gets the errors
>>
>> configure: libxrandr development files not found, XRandr won't be supported.
>
> This is precisely part of the problem with -Werror.  You've now caused
> some configure checks to fail that, presumably, were passing before.
> Are they worth making warning-free?  Some of the warnings may be in
> headers we don't control.  What do we do then?

You're pretty negative on this idea, aren't you?  Let me whittle away at
it a bit before we reject it as impractical.

>> And if one blows past those, "make depend" fails.  In fact, everything
>> fails pretty spectacularly.
>
> So a broken config leads to a broken compile?

No, there seem to be multiple severe breakages not caused by the
slightly broken config.
But let me gather some more data.
- Dan