removed the limit on the read buffer size until I fully understand the

removed the limit on the read buffer size until I fully understand the
interactions with ssh. The old ssh freezes have shown up again and
some debugging (with help from James Welborn) showed that the cause
was the read buffer hitting maximum size. I think this means that ssh
must be misbehaving about blocking IO.

This change gets rid of the freezes at the expense of memory
usage. Where it would have frozen it uses more memory instead.