Major Description
The FSTs produced by Builder can be further shrunk if you are willing
to spend highish transient RAM to do so... our Builder today tries
hard not to use much RAM (and has options to tweak down the RAM usage,
in exchange for somewhat lager FST), even when building immense FSTs.
But for apps that can afford highish transient RAM to get a smaller
net FST, I think we should offer packing.