Fix the incorrect value of $host when IPv6 in Host header

[Maxim Dounin]

Hello!

On Wed, Aug 31, 2011 at 03:46:50PM +0800, Speed First wrote:

> This is the diff to fix the problem of
> http://forum.nginx.org/read.php?2,214541
> 
> Can this be integrated into main branch? Thanks.

This patch isn't enough, please see
http://trac.nginx.org/nginx/ticket/1

Additionally, it's not really correct: it hides the logic under 
#if, while this should be supported even without ipv6 compiled in.  
The ticket in question links to a bit better patch (which still 
not enough though).

Maxim Dounin