Fix Trac #43 again.

stream.lisp:
o Remove the old code that was the first attempt at fixing issue #43.
  This was wrong.

fd-stream.lisp:
o Fix issue #43.  Even if we have a string-buffer, we need to take
  into account any octets in the in-buffer (if it exists) that have
  not been processed.  This happens if the in-buffer does not have
  enough octets at the end to form a complete character for the given
  encoding.
o Some debugging prints added, but disabled.