Patch to compile squid 2.2pre1

Dear squid-users,

here's a small patch to make squid 2.2pre1 compile on my
i586-pc-linux-gnu system.

There seems to be a problem with async io on linux using
pthreads. After I start squid it eats 99% CPU time and does nothing.
Even telnet to port 3128 doesn't work. This patch is not a fix for
this particular bug. I just wanted to report it and will try to
submit a reasonable bug-report this afternoon.

cheers,
Patrick