(But it won't work on some systems without IPv4/IPv6 localhost
(some BSD jails) by design, to avoid creating sockets on routable
IP addresses. However, those systems likely have the AF_UNIX socketpair,
which tor prefers.)

Fixes bug #17638; bugfix on a very early tor version,
earlier than 22dba27d (23 Nov 2004) / svn:r2943.

Patch by "teor".