Changes

• CI status badge now to points to GitHub Actions, no more Travis-CI
• Silence some developer debug messages
• Always skip . and .. in FTP listings
• Internal refactoring and code cleanup

Fixes

• Fix mdoc warning, found by lintian
• Fix regression introduced in v2.14, server directory name shown in FTP
  listings instead of ., e.g. MLST . showed the directory name
• Fix #36: for real this time, now also with a test case to verify
• Fix #38: duplicate entries in FTP listings, regression in v2.14.
  Caused by (initially unintentional) removal of sorted listings, where
  directories prior to v2.14 were listed first. This change, albeit an
  accident, actually helped clean up the code base and speed up replies

Packages for Debian 10, and compatible Ubuntu releases, available at https://deb.troglobit.com/