signature MLTON_PROC_ENV =
   sig
      type gid
      val setenv: {name: string, value: string} -> unit
      val setgroups: gid list -> unit
  end
- 
setenv {name, value}
like the C setenv function. Does not require name or value to be null terminated.
 - 
setgroups grps
like the C setgroups function.