SIGALRM not caught in mainloop_poll()

Hello,

Further to my modifications of pen in mainloop_poll() yesterday, we've
noticed that the SIGALRM handler is initialised only in
mainloop_select(), and not mainloop_poll(). This leads to pen dying
with 'Alarm clock' if a backend server ever fails.

I couldn't see much point in doing it all twice, so I moved the
instructions from mainloop_* into main() before the chosen mainloop is
called, as per patch:

http://spork.qfe3.net/pen/pen_signals_chrise_20051213.diff

-- 
Chris