Defer "PreferIPv6 by default" to 0.4.4

In legacy/trac#32637 (moved), we made clients default to "PreferIPv6" on SOCKSPorts (and other client ports).

But in legacy/trac#33796 (moved), we discovered that this change broke torsocks.

We want to defer this change to 0.4.4, so tor can implement IPv4-only and IPv6-only resolves for torsocks.

Since legacy/trac#32637 (moved), we have also merged:

• legacy/trac#33608 (moved), which removes a forced PreferIPv6 for non-SOCKSPorts
• legacy/trac#32994 (moved), which puts the PreferIPv6 default in port_parse_config(), rather than in 2 different places in the code

So it should be very easy to change the default for PreferIPv6.