Yank a whole load of computation out of the edgepoint shape geometry shader.  Not done yet; comparing with adjacent edge points (as opposed to properly vapour-adjacent hypothetical points) produces bad results ...
Pure points edge shape.  I've introduced a horrible bug by doing this, see the TODO in shape_edgepoint_vertex :(
Big pile of jigsaw access fixes that ought to sort it out, yet mysteriously don't.  This is such a mess.  Also I think I should port some of those changes to master, etc etc...