configure.ac: add -Werror to default compiler options

[Dan Kegel]

On Fri, Sep 19, 2008 at 1:17 AM, Alexandre Julliard <julliard at winehq.org> wrote:
> A compile failure is a serious bug, and we should do everything
> possible to avoid them.

Agreed, to an extent.   A user who is trying to compile with a really
whacky toolchain (say, a C compiler on an Amiga, a mainframe, or a wristwatch)
should expect some errors, and we should not try to avoid those if they reflect
real problems that need to be solved before wine can run properly.

And I also feel pretty strongly that compiler warnings have
some value, and we should pay attention to them.  Right
now we're plugging our ears and going "la la la la la I can't hear you",
and that seems a bit careless.   As Wine aims for higher and
higher quality levels, eventually we will have to change our ways here.

> Making -Werror the default is the worse thing we could do in that respect.

If we do it in the right way, it could end up increasing
our code quality quite a bit without inconveniencing any users.

The right way is to slowly fix all the warnings -- like Andrew Talbot
is doing --
and slowly encourage all wine developers to crank up their warning
levels to the max.  Once we've voluntarily cleared out nearly all the
warnings, we can then have a flag day to clean out all the rest,
and switch -Werror on.  That will keep errors from creeping back in.