where are all these magic flags and variables documented?

even the oldstyle POSTFIX_USE_* flags don't appear in mk.conf(5) nor
anywhere in the 2.0 source tree on my 2.0_BETA machine.

I'd RTFM if I could find it...

-- 
  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