bug#20254: 25.0.50; `face' overlays with equal priority at the same location

[Stefan Monnier]

>> > Any chance this implementation could be revisited, to do something
>> > regular
>> Without explicit priority information, we have no data on which to base
>> the ordering.
> Order of creation.  Newer replaces or dominates older.

We don't keep track of order of creation.  So this would require adding
a counter to every overlay (which in turns means increasing the size of
overlay and marker objects from 6words to 8words).
Doesn't seem worth the trouble, since while it does provide some form of
reproducibility, it doesn't give much control.


        Stefan