-Wnetbsd-format-audit for extra-stringent format checking.
WFORMAT belongs in individual makefiles and/or Makefile.inc files.
FORMAT_AUDIT should go in mk.conf if you're doing format-string auditing.
(set WFORMAT=1 in individual makefiles if a program is
not security critical and is doing bizarre things with
format strings which would be even uglier if rewritten)
FORMAT_AUDIT may go away in time (i.e., default to on)