Log Message:
pkgtools/pkglint: update to 5.6.1

Changes since 5.6.0:

* Fix output of relative paths in the diagnostics (thanks @wiz)
* Fix parsing of ${VAR:ts---}; it is now a syntax error
* Load more type definitions from mk/* instead of hard-coding them
* Lots of refactoring to improve test coverage, fixing several
  small bugs as they were found