sys-apps/portage: version bump to 2.3.9

sys-apps/portage: version bump to 2.3.9

Fixed bugs:

  #627106 - Add DOCS to environment blacklist
  #628386 - dev-python/pycparser-2.18 breaks "ebuild" command
  #629010 - Ban get_libdir in global scope
  #629146 - RepoConfigLoader: Fix compatibility with Python 3.7
  #629148 - gnome2-utils postinst: Restrict file types for false positives
  #630538 - Fix emerge --info when using webrsync (regression)
  #630730 - AsynchronousLock: missing dummy_threading for Python 3.7

Package-Manager: Portage-2.3.9, Repoman-2.3.3