text-formatting: fixes for INDENTING-OUTPUT-STREAM
text-formatting: fixes for INDENTING-OUTPUT-STREAM

* The code used internally to detect line starts is provided as
  a STREAM-START-LINE-P method.

* INVOKE-WITH-INDENTING-OUTPUT first indents by adjusting the cursor
  position of the underlying stream, calls the continuation, then
  dedents by adjusting the cursor position by the same amount but in
  the opposite direction. This way, non-text output such as tables or
  graphics are affected consistently by the indentation.

* When newlines are output (embedded in strings or via the character
  #\Newline), the indentation is applied to the underlying stream after
  outputting the character or text segment. This is necessary for
  consistency with the initial indent and final dedent described
  above.

slyrus/mcclim,slyrus/mcclim