Erik Rungi's ntserv/socket.c modifications

[Dave Ahn <ahn@vec.wfubmc.edu>]

I've looked over and tested the socket.c changes by Erik Rungi
<rungus@openface.ca> submitted a while back [VANILLA-LIST:2246].
Since many modern firewalls do in fact let internally initiated
UDP connections to be established through the firewall, I think
it makes sense to enable this new code in the server by default.
The changes will be committed shortly.

Fortunately, these changes don't break backwards compatibility for
any clients that don't have the USE_PORTSWAP code enabled.  I
know that COW and Paradise derived clients have the code; I'm
not sure about BRMH.

The next round of TedTurner clients will enable the USE_PORTSWAP
code as a runtime option.  I'd recommend COW be updated similarly.
But note that you shouldn't just #define USE_PORTSWAP on the client
side blindly, because it will break UDP connections to 2.9pl2 servers
or earlier.

FYI, pickled.fox.cs.cmu.edu 1111/2222 test server has this new code
installed.  Try it out if you're behind a firewall.

Dave, who is looking forward to UDP without tunneling X...
-- 
Dave Ahn <ahn@vec.wfubmc.edu>        |  "When you were born, you cried and the
                                     |  world rejoiced.  Try to live your life
Virtual Endoscopy Center             |  so that when you die, you will rejoice
Wake Forest Univ. School of Medicine |  and the world will cry."  -1/2 jj^2