configure.ac: add -Werror to default compiler options

[Francois Gouget]

On Fri, 19 Sep 2008, Dan Kegel wrote:
[...]
> So my alternate suggestion is for patchwatcher to reject patches that
> fail with -Werror.
> (And work around the couple of bogus errors I listed above.)

It does not even have to build with -Werror, just to grep the log for 
warnings, and warn if there are new ones.

The benefit is that because the compilation succeeded, you still get to 
test the patch for other errors, notably by running the conformance 
tests. Then the patchwatcher report can complain about both warnings, 
and any conformance regressions that it identified.

In fact, we could even have patchwatcher compile with multiple 
compilers, a bleeding one and an older one, gcc 2.95 say, so we catch 
these nameless unions earlier ;-)
(but I don't mind continuing with my weekly gcc 2.95 build)


-- 
Francois Gouget <fgouget at free.fr>              http://fgouget.free.fr/
        It really galls me that most of the computer power in the world
                          is wasted on screen savers.
                     Chris Caldwell from the GIMPS project
                       http://www.mersenne.org/prime.htm