p5-Device-Modem: update to 1.59.

1.59  Mon Jun 15 08:17:54 CEST 2020
    - Merged pull request #6 from ghciv6/fix_multi_instance_log
    fixed log handling with multi instances and typo in close().
    Thanks to @ghciv6 !

1.58
    - Updated test suite a bit.
    - Added the tests to the manifest.
    - Got rid of indirect object syntax.
    - Moved test.pl to the actual test suite.
    - Updated $VERSION declarations according to:
      http://www.dagolden.com/index.php/369/version-numbers-should-be-boring/
    - Added some extra tests (xt/author, xt/release).
    - Fixed some spelling.

(wiz)