bug#17234: 24.3.50; overlay priority : cons cells make an error in ediff

[Stefan Monnier]

> That makes an error
>> Wrong type argument: number-or-marker-p, (nil . 100)
> in function ediff-highest-priority, which comes from commit

Indeed, thanks.  Ediff's handling of overlay priorities is a good
example of what's wrong with overlay priorities, adding code to
make sure its overlays are "on top", then adding yet more code to ensure
its other overlays are "even more on top".  And then yet more code to
try and defeat the other packages which might be taking part in this
race to the highest priority.

So, I just threw it out, which should solve those problem.


        Stefan