Consider renaming fs_mistrust make_secure_dir
I noticed a call to this function when reviewing !483 (merged). I think the name is a hazard, in that it seems to imply a more general "magic security sprinkles". (I vaguely remember a conversaton about this but perhaps it was only on irc; in any case I haven't looked for it.)
@nickm, if it was decided to keep this name and I have forgotten that, please forgive me.