* Fix bug in INPUT-BUFFER/DISCARD-CHAR: was not doing anything if the

* Fix bug in INPUT-BUFFER/DISCARD-CHAR: was not doing anything if the
  input buffer was empty.

* Change INPUT-BUFFER/READ-SUBSTRING to read a whole buffer from the
  input channel if the required number of characters is less than the
  size of the buffer.

* Change INPUT-BUFFER/READ-SUBSTRING to continue reading from the
  input channel until the substring is filled or the channel has no
  more characters available.  This is a correct fix for the change
  made in revision 14.47; this fix does a probe of the channel to
  determine if there are any characters immediately available.
  Previous to 14.47 the procedure might have blocked waiting for input
  that was not ready, even if it had already partly filled the
  substring.  Now it will immediately return any characters that are
  available, and block only when nothing is available.