Added DualStack support for using a IPv6 Socket to listern to IPv4 connections.

Added support for dual stack sockets in cSocket and added use of Dual stack sockets as an option in Webadmin and RCONServer (defaults to false). 
I'll do Server next.
Also can someone with VS 2008 and windows XP (xoft :smile: ) test this on windows as I'm not definat about the header I'm using to warn if you attempt to enable it on xp.

Fixes #189