[MERGE][0.16] fix problem with SIGQUIT on win32

[Martin Pool]

On 4/25/07, Alexander Belchenko <bialix at ukr.net> wrote:
> >     if os.environ.get('BZR_SIGQUIT_PDB', '1') == '0':
> >         return
> > +    if getattr(signal, 'SIGQUIT', None) is None:
> > +        return
> >     signal.signal(signal.SIGQUIT, _debug)
>
> Well, either variant is OK for me.
> But documentation on signal module talk preferable about Unix.
> I don't know is signal standard library could be useful at all on win32.
>
> OK, I'll change as you suggested and merge with PQM.

Actually after thinking about it more I think your original suggestion
of checking sys.platform is better  because it's the same condition
used in the tests.

-- 
Martin