Leaving opacity-mask or symbol editing now removes the editing layer
wherever it is, so a save or export after Layers moved it into another
layer no longer writes it. An editing id that names anything other than
a layer is left alone.
symbol_edit is no longer read from files: a value in file data is
dropped on load, so the layer it names is kept and saving does not
write the value again.
A save with precision rounded the tier-1 Intertwine area but left the
areas of tier 2 and up exact. The format test now gives the object a
tier-2 area too, and sets the symbol's new dynamic field.
dotCooCoo