[PATCH 04 of 10 ipv6 V2] tinyproxy: use IPv6 if HGIPV6 is set to 1

[Jun Wu]

Excerpts from David Soria Parra's message of 2017-02-21 09:29:50 -0800:
> [...]
> 
> I think my point is that the correct thing to do, is to bind on v6/v4 if
> available at all times (that includes hg serve, i look into this) instead
> of make it a switch, as that would defeat the address resolution rfc.

Got it. If "hg serve" is changed to bind on both, run-tests could be updated
accordingly. However "hg serve" is outside of my plate for now.