This undoes commit 5764, which was ill-considered. We already had incremental
prints at that point to 'last_run'. As long as we don't run out of RAM
on large traces, there doesn't seem any need to print to stderr.
Now '--dump' is only needed when juggling multiple traces.
This undoes 5672 in favor of a new plan:
Layers 000 - 099 are for running without syntax sugar. We use them for
building syntax-sugar passes.
Layers 100 and up are for running with all syntax sugar.
The layers are arranged in approximate order so more phases rely on earlier
layers than later ones.
I plan to not use intermediate syntax sugar (just sigils without calls,
or sigils and calls without braces) anywhere except in the specific passes
implementing them.
Kartik Agaram