Upstream changes:
2.006003 - 2019-03-10
- releasing as stable
2.006_002 - 2019-01-29
- Fix quotifying of backslashes in utf8-flagged strings on perl 5.10.0.
2.006_001 - 2019-01-07
- avoid warnings or failures on new perls when testing quoting UTF-8 strings
- test quotify output under utf8 pragma
- fix quoting of negative NaN
2.006_000 - 2018-12-29
- don't test threads behavior on perl < 5.8.5, since they are too unstable
- more tests
- preserve inf, nan, and false in quotify
- improve accuracy of quotified floating point numbers
- SUB_QUOTE_DEBUG can now be set to sub names, package names, or a regex to
match against the code to filter which generated subs are printed to STDERR.