Update to 2.04

Upstream changes:
2.04  2019-05-24

- Add a partial workaround for "Bizarre copy" errors (GH #11) that come when
  attempting to look at arguments in the call stack. This is only a partial
  fix as there are cases that can lead to a SEGV. Ultimately this needs to be
  fixed in the Perl core. See
  https://rt.perl.org/Public/Bug/Display.html?id=131046 for relevant
  discussion. Fixed by pali. GH #21.

(wen)