Scaling to 10^6 clients

I just tested the server with 10^6 clients generated by a perl script. After fixing an O(N^2) issue in conffile.c, it now takes ~8 seconds on my machine to start up. That's a little slow, but mostly tolerable. It's response to packets is pretty much instantaneous, though. So the recent changes to make client lookups O(ln(N)) appear to have helped. Alan DeKok.