Tests seem to be broken

[Karsten Poeck]

The tests in https://github.com/gwkkwg/trivial-backtrace/blob/master/test/tests.lisp seem to be broken:

• probably https://github.com/gwkkwg/trivial-backtrace/blob/master/test/tests.lisp#L19 should read :(addtest (generates-backtrace)
• why should
  (with-output-to-string (stream) (print-backtrace c :output nil))
  return a string? Print-backtrace returns a strings, nothing is printed, so the result is ""

[gwkkwg]

Thanks for your fixes. I'm not longer doing Lisp development. If trivial-backtrace interests you, I'd be happy to turn the project over to you.