Try and improve the print-backtrace-and-exception/knots output, be
selective about the stack frames which are shown to try and produce
some useful output which reflects user code and hide the
&knots-exceptions.
This commit also introduces a bunch of tests scripts that produce
output from print-backtrace-and-exception/knots, to help test this
code in different situations.
Which call put-bytevector for performing output. When used in
combination with an unbuffered port, this should be safer than using
the normal Guile procedures, as I think it'll avoid writing to the
buffers, while still avoiding single character at a time output.
More research is needed though in to how to output to stdout/stderr
when using fibers with a parallelism greater than 1.
