make IPv6-only clients bootstrap without needing config changes.
legacy/trac#17281 (moved) suggests that an IPv6-only client should be able to bootstrap by setting some flags in torrc. I've done:
ClientUseIPv4 0 ClientUseIPv6 1
But, most clients are not always IPv4-only or IPv6-only. In particular, i tend to move my laptop between networks that have different properties (i'm writing this from a v6-only network).
I shouldn't have to fiddle with my torrc to make tor work. it should be able to auto-detect this situation and do the right thing automatically.