Multi-threaded OpenSSH

The Teragrid (http://www.teragrid.org) uses The HPN patch for all of its clusters as the
window resizing makes a big difference in long-haul scp transfers, e.g. NCSA to SDSC.

I wasn't aware of the multithreading, but I'm not thinking that any of the current clusters
have single cpu boxes, so that might be helping as well, as all of the nodes would have the
extra cpus for use.