What OSes are officially supported by pkgsrc?

(IE am I wasting my time filing PRs for problems with pkgsrc and NetBSD
1.4.3A?)

-- 
  Aaron J. Grier | "Not your ordinary poofy goof." | agrier@poofygoof.com
  "someday the industry will have throbbing frontal lobes and will be able
  to write provably correct software.  also, I want a pony." -- Zach Brown