[9fans] Native TCP/IP stack in 9vx working

["Devon H. O'Dell" <devon.odell@gmail.com>]

Hey everyone,

Over the past few days, Erik Quanstrom has been helping debug issues
with the native IP stack in 9vx. He figured out some crazy issues with
gcc wanting to return negative values for signed modulo comparisons --
this combined with a stupid oversight has got IP working. Erik says
he's moving IL in tomorrow -- at this point, that shouldn't be a huge
deal.

Linux seems to have better performance than FreeBSD/Darwin -- this is
because Linux lets you read TCP/UDP over a raw socket. BSD platforms
don't let you do that -- you have to use BPF for this -- and libpcap
makes that a bit easier -- so I think there's a bit more overhead
involved with that.

Also, there's still a fair amount of probably useless debugging stuff
that we could conditionalize at compile-time, but I'll leave that in
for a while before that happens.

Please test it out!

http://testbed.dh0.us:8000/

Big thanks to quanstro for his huge help in debugging.

--dho