Hey,
We've been meaning to split net.c up for quite a while now,
so here goes with a first cut at.
There shouldn't be anything too controversial here, apart
from CONFIG_LINUX maybe.
I've build tested this on F11, F12 and mingw and also done
some basic runtime testing.
Building on e.g. *BSD, Solaris and AIX hasn't been tested.
I wouldn't be surprised if I've broken the build there despite all
my efforts but, if I have, it should be trivial to fix back up.
This isn't the end of the cleanups; obviously the other
backends could be split out too, we could use module construtors, etc.