Log Message:
devel/pkgconf: Update to 2.2.0

Changelog:
Changes from 2.1.1 to 2.2.0:
----------------------------

* libpkgconf SOVERSION is now 5.

* Significant solver rework to flatten both requires and requires.private
  dependencies in a single pass.  Improves performance slightly and ensures
  proper dependency order.
  Patches by Kai Pastor.

* Improve `--digraph` output to reflect more of the solver's state in the
  rendered dependency graph.
  Patches by Kai Pastor.

* Do not reference the graph root by name when presenting error messages about
  directly requested dependency nodes.
  Patch by Kai Pastor.