electronic submission
---------------------
 * do we want *ar* to be got working across Linux vs. FreeBSD, since tar
	needs such elaborate precautions?
	(show precautions business to Silvana; and indeed in principle to
		all TAs who maintain an electronic submission system.)

 * open-ended filename structure at submit/autotest-time?

 * what about submission of *directories*? Note that because of the ridiculous
	security holes in tar documented in the comments in receive_submission
	(i.e. the tricks with chains of "../" and/or symlinks), it's *not*
	just a matter of saying "let it all unpack if it's a directory"!