doc for svn and firewalls are missing

[Bjarni]

somebody should write how to use svn if the default port is blocked by a firewall.
it should be added to
http://www.openttd.com/development.php

I found openvpn, which is crossplatform and seems to do the job, but I have not tested it, since I don't have the problem

http://openvpn.sourceforge.net