Bug 13252 - SIP2 server should accept IPv6 connections

Bug 13252 - SIP2 server should accept IPv6 connections

This small patch adds a check on the SIP2 socket connection if it is
IPv6 and resolves socket address accordingly.

Any newer Debian distro would probably default to IPv6 so it would
eventually affect all SIP servers.

Tests against running SIP server on an IPv6 box:

http://wiki.koha-community.org/wiki/Koha_SIP2_server_setup#Testing_with_Telnet

before patch:
  disconnects immediately. Log output:
  Bad arg length for Socket::unpack_sockaddr_in, length is 28, should be 16

after patch:
  operates normally

Signed-off-by: Colin Campbell <colin.campbell@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>