configure.ac: add -Werror to default compiler options

[Francois Gouget]

On Thu, 18 Sep 2008, Rob Shearman wrote:
[...]
> > engine.c:500: warning: 'hres' is used uninitialized in this function
> 
> Or it could just be that they had a different compiler version to you
> and so the warning didn't appear for them. This is the trouble with
> using -Werror in an uncontrolled environment

Maybe patchwatcher could detect new warnings (e.g. using git-blame as I 
described before) and either flag the patch outright as incorrect, or 
give it an intermediate state between bad patches (those that don't 
compile or cause test regressions) and good ones (that compile and don't 
cause test regressions).

In either case it would be good to run the conformance tests on such 
patches anyway so the submitter can fix both the compilation warning and 
any test issue in one roundtrip.

-- 
Francois Gouget <fgouget at free.fr>              http://fgouget.free.fr/
        A polar bear is a cartesian bear after a coordinate transform.