Oops, forgot <stdarg.h>. PR 48037

There must be something wrong with netbsd's headers, as none of

  #include <stdbool.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <errno.h>
  #include <err.h>

ought to leak in stdarg.h, but apparently one is.

(dholland)