Fixup IPv6 Listen statements on Linux by attempting to bind in the order

that getaddrinfo() returned to us and skipping binding to IPv4 addresses
if the previous bind was to an IPv6 of the same address and port.

Justin made some style changes, added a (struct in6_addr*) to make it compile
on *BSD as well as an attempt to make the addition of the listener to the list
a little more efficient.

Submitted by:	Colm MacCarthaigh <colm@stdlib.net>
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@101083 13f79535-47bb-0310-9956-ffa450edef68