sftp performance problem, cured by TCP_NODELAY

[Miklos Szeredi]

> > Done.  Can I now have my NODELAY please ;)
> 
> Got a syscall and packet trace showing "the right thing" being done?-)

Can send it tomorrow.  But the best indication that it's right is that
the performance problem is gone.

I don't know how far 4.3 is in the freeze state, but unconditionally
setting NODELAY seems quite safe.  It is bound to drastically improve
performance for many people, while any noticable performance
regression is highly unlikely.  But anyway I leave that to you guys to
decide.

Miklos